^^ What they said...
So, what I think you need to know is:

1) What's your monthly saving going to be by switching accounts. And assuming rates stay the same, what would you save over the term of your current mortgage (upside)
2) What will you be charged by your current lender for switching (% penalty and early repayment fees)
3) What will the new lender charge you (arrangement fees - could be £500+, legal fees, survey)

If 1 is greater than 2 plus 3 then it may be worthwhile, but if it's not by a lot, then consider the impact in terms of hassle - it could be more trouble than it's worth. In my case is was worthwhile as it let me pay off my mortgage several years early.

For saving money, it might also be worth thinking about changing energy suppliers, home insurance, car insurance, and so on - if if you're doing that - don't forget to do it via one of the cashback sites.

Always worth a look on moneysavingexpert.com for these sorts of thing.

EDIT: Don't try to do mathematical functions in posts kids, it took me 4 attempts to get this one up here, and I eventially had to write it out longhand...
( Fireflier La la la la, not listening on, Tue 11 Aug 2009, 10:26, Reply)