To flex or not to flex

I have been trying out various estimate and quote services online for current account mortgages (for example First Direct, Virgin, Intelligent Finance) and all seem to be telling me l can save thousands of pounds and pay off my mortgage early. I know that interest rates on these mortgages are often not as competitive, but is there a big obvious downside l am not seeing and these websites are not telling me about?
- JD, Fulham

The principle of a current account mortgage is that it is linked to a bank account. Money in that bank account is offset against the outstanding mortgage loan and you thus receive interest at the mortgage rate, which is normally higher than the bank account rate. In theory you are therefore saving money.

Much bigger savings are available if you are able to pay off some or all of the mortgage early. However both saving advantages presuppose that you have surplus cash available either to hold in your bank account or to reduce the mortgage.

That seems unlikely bearing in mind that you are borrowing, usually up to the hilt. You have to consider whether it is worth paying a higher mortgage interest rate for the extra flexibility

· John Edwards is a financial journalist, formerly personal finance editor at the Financial Times.