Sir KDM,
I take your point about the 30% deposit, but if your flat is paid off over time, you are always in profit regardless of whether the price has gone up or down. The up and down just determines the level of profit, not whether there is one or not. The alternative would be to keep the flat and let it out to give you retirement income. Admittedly it may take up to 15 years to pay off a large mortgage, but it takes even longer to build up a decent pension fund.