Offset Mortgages
The basic idea of offset mortgages is that any money you have in credit is offset against the mortgage, which will reduce the amount of debt on which interest is calculated.
Pros
If you have a decent amount of money in savings you really can save a lot of interest on the loan, pay it off quicker than usual and become mortgage-free far earlier than you might expect.
If you get bonuses or large lumps of money every now and then, you can put it straight into your mortgage without penalties.
If you run short of money quite regularly, you can draw on any of your mortgage that you have already paid.
If you are married or cohabiting, you can put both your salaries into the offset account.
Cons
The mortgage rate is usually not the most competitive.
Many other, non-offset mortgages are now thoroughly flexible and offer, for example, an easy way to overpay with a lower interest rate.
If you tend not to have much in the way of savings you will save very little interest over the term of the mortgage.
The temptation to constantly draw against your mortgage can be too much and you will end up never paying it off.