When your fix ends you have two exits: a new deal with your current lender in ten minutes, or a full remortgage to whoever's cheapest. The right answer is a number, not a preference.
The comparison
Product transfer (same lender)
Remortgage (new lender)
Speed
Minutes to days
4–8 weeks
Affordability check
Usually none (like-for-like)
Full application
Legal work / valuation
None
Needed, often free with the deal
Rates on offer
Your lender's retention menu only
Whole market
Fees
Usually £0 (product fee optional)
£0–£2,000 all-in, varies by deal
Borrow more / change term
Limited
Full flexibility
The 0.2% rule of thumb
Effort has a price. On a £200,000 balance, each 0.25 percentage points of rate is roughly £25–30 a month. So:
Market beats your lender's offer by less than ~0.2% → take the transfer, keep your afternoon.
Market wins by more than ~0.2–0.3% → the remortgage typically pays for its paperwork many times over on a 2–5 year deal.
Balance under ~£100k → raise the threshold; the same rate gap moves fewer pounds.
Your finances look worse on paper than last time. Newly self-employed, income down, missed payments, maternity leave: like-for-like transfers usually skip the affordability check a new lender would run.
You're selling within a year or two. Shorter horizon, less to gain, and some transfers carry lower or no ERCs early on.
The clock has run out. Deal ends next week? Transfer now to dodge the SVR; a full remortgage can still follow later — but check the new deal's ERCs before planning a double-switch.
When the remortgage wins beyond rate
Your LTV band improved. If your home's value rose or the balance fell through a 75% or 60% loan-to-value threshold, the whole market reprices in your favour — retention menus often don't reflect it fully. A remortgage triggers a fresh valuation.
You want structural changes. Borrowing more, shortening the term, adding or removing a name — transfers handle these poorly or not at all.
Do both, pay for one
Nothing stops you getting your lender's transfer offer (ten minutes online, no commitment) and a whole-of-market quote from a fee-free broker, then choosing. Lenders count on you not comparing; comparing is the entire job.