What we did in the US was to buy a house that was less than we could afford then make an extra payment on to the principle each month. E.g. an extra $100 per month would chop off seven years and save a large amount of interest. If our income ever dropped it would be the first thing to stop doing as it was optional.
However, when we got a mortgage here we found that during the fixed period (five years for us) extra payments were not allowed. I don't know if this is standard across all lenders in the UK but it is pretty crummy. When shopping around it might be worth asking if there are any "pre-payment penalties".