My flight app,
Alas not limited to Britain by any stretch of the imagination.
I looked at buying an iPad2 from Sydney dutyfree where they now have an Apple Store airside in the International Terminal.
I stupidly assumed that the price would be current retail less GST (10% in Australia = Minimum AU$55 discount). When i checked the price at the airport it was only $15 less than retail.
In many respects you are probably better off trying to win in the currency game if flying afar or finding someone that could buy you one via the Apple Schools program.
Hope it helps.