Balance-transfer offers look irresistible on paper. The honest analysis has three inputs: rate differential, remaining tenure and switching cost.
As a rule of thumb, a transfer merits serious evaluation when the rate differential exceeds 0.35–0.50% and meaningful tenure remains. Processing fees, legal and valuation charges, and stamp duty on the new mortgage all eat into savings.
Run the break-even: total switching cost divided by monthly interest saving gives you the months to recover cost. If you may prepay or sell within that window, stay put.
Also consider the soft factors — a top-up requirement, service quality, and whether your current lender will simply match the offer if asked. Often, a repricing request is the cheapest transfer of all.