Brokers say mortgage holders are contacting them six months early as they are "worried about payment shock" over fixed rate rises. Over the past 12 months, UK searches for "fixed-rate mortgage" have more than doubled, up 109%, according to Google data.

Searches for "Bank of England base rate" have fallen 15% over the same period. Searches for "remortgage" are up 53%.

UK Finance says 1.8 million fixed deals ending this year, after 1.6 million last year. On Thursday, the Bank of England held at 3.75% for its base rate for the sixth time, while fixed-rate mortgages continue to rise. Brokers agreed that clients were contacting them earlier over fears of mortgage rates increasing.

Nick Gatti, mortgage adviser at NG Mortgages, said: "100% we’re seeing this, more than usual too. We’ve seen a surge of customers getting in touch five, six, even seven months before their current fixed rate ends. Especially those coming off sub-2%, five-year fixes.

"It’s not the wrong thing to do either. Especially with a lot of lenders reducing the lead time on their product switches to three or four months. The plan for most now seems to be get everything prepped as early as possible, lock in a new rate at bang on six months and then, most importantly, watch the market.

"If the rates keep going up, then great, they’ve locked in at the best time. If they go down, they can usually hop over to a cheaper rate as and when it becomes available, before their current deal ends. At the end of the day, starting early just gives them more options."

Tracey Dixon, buy-to-let mortgage specialist and owner at Cardiff-based Pure Mortgage and Protection, agreed.

She added: "Clients are contacting me four to six months before their fixed deal ends because they are worried about payment shock, not just the headline rate. They want to know what their next mortgage could cost and how it will affect their monthly budget.

"Many still assume a Bank Rate cut automatically means cheaper fixed mortgages. It does not. Fixed rates are influenced by swap rates, lender funding costs and competition, so they can rise even when Bank Rate is held.

"Starting early does not mean committing immediately. It allows borrowers to understand their options, secure a suitable deal where appropriate and continue reviewing the market. Starting early creates choices while waiting until the final few weeks removes them."

Ross Lacey, director and Independent Financial Adviser at Rayleigh-based Fairview Financial Management, said clients never used to contact him as early as they were now.

He added: "We get in touch with clients proactively six months before their current mortgage deal ends. Go back a couple of years, and people were often surprised we spoke that far in advance. Now, we have clients contacting us more than six months ahead, asking what their options are, concerned about rates.

"There are still a number of people on very competitive fixed rates starting with a '1' or '2'. Part of our role is to prepare them for the new rate and look at ways to soften the blow of higher monthly payments.

"We'd advise getting a deal locked in as early as possible, then reassessing how rates move in the lead up to existing deals ending. That way, better rates can be locked in if they come up, but there's protection should they worsen."

Harry Goodliffe, director of Winchester-based HTG Mortgages, said nearly two million people were in for a shock.

He added: "People aren't scared of the Bank of England anymore. They're more scared of the letter from their lender. Clients ring me six months out, sometimes more, and hardly any of them will ask about the Bank of England. They ask what their new payment will be.

"The bit I end up explaining most weeks is that a base rate hold doesn't mean your fix stays put. Rates have jumped in a month while the Bank did nothing. With 1.8 million deals ending this year, that's a lot of people who could be in for a shock."

Manooch Suree, director of Uxbridge-based Zinga Financial Services, said the Bank of England holding did not mean fixed rates will stay the same.

He added: "A lot of clients still believe fixed mortgage rates are driven solely by Bank of England rate decisions, which simply isn’t the case. We often have to explain that fixed rates are influenced by several factors, including swap rates and lenders’ funding costs.

"We’ve always contacted clients six months before their deal ends, but we’re now finding more are willing to secure a new rate earlier rather than wait and see. The biggest concern is increasingly uncertainty rather than short-term rate movements. We’re also seeing more clients choose five-year fixes over two-year deals because they value knowing what their payments will be for longer, particularly while the economic outlook remains uncertain."

Michelle Lawson, director of Fareham-based Lawson Financial, said she had clients coming off 0.99% rates and being met with rates five times that.

She added: "People are worried and budgets are squeezed by the day. Fixed rates are rapidly rising due to the coninuef instability in the Middle East and a Government that is way out of control of its own budget management.

"Early intervention is best – if your broker is getting in touch, don’t ’wait and see’ as this could be costly. Something has to give, borrowers are panicking. Just yesterday I had customers coming off 0.99% fixed rates and being met with rates five times that."

Richard Davidson, mortgage advisor at onlinemortgageadvisor.co.uk, said many were still hoping for rate reductions in the future.

He added: "Most of the people I speak to aren't coming to me early. They're hanging on in the hope that rates will be lower in a few months and for the past couple of years that hope has been wrong. The Bank held rates again this week and fixed deals have still crept up, because lenders price fixes on what markets expect over the next two or five years, not on what the Bank did on the day.

"If your deal ends within six months, book something now rather than waiting for a cut that may never reach your rate anyway. Most lenders will let you move to a cheaper deal if rates fall before you complete, so locking in early protects you if they rise and costs you very little if they don't."