First Active has been the main promoter of Offset mortgages in recent years and they have had quite a degree of success.
But what is an Offset Mortgage?
The simple explanation is that your mortgage account is in effect combined with your current account. Any credit balance on your current account is used to reduce your monthly interest costs on the mortgage, i.e. you are offsetting the credit balance on your current account against the debit balance on your mortgage.
And are they a good idea?
In some cases yes, in others no. As usual, no easy answers in financial services 
The simple rule of thumb is that the higher the balance that you usually hold in your current account, the more you will be benefit from an offset mortgage. However, the interest rate applied on an offset mortgage is typically higher than the standard tracker rate on offer, so if you tend to carry a low current account balance you are likely to end up paying more.
Also, the amount of money you are borrowing will decide how much you would need to continually have in your current account in order for the offset mortgage to represent good value for you.
