They haven't. Most people measure it on the basics. A loaf of bread is pretty much double what it was 10 years ago, you can't buy a decent loaf of bread for less than £1. Who shops in Aldi and Lidl? Despite what people think they aren't that much cheaper than anywhere else and you often end up buying brands nobody has heard of: Dorkers Crisps, Dr Popper.
Bread:
The current spread is from 62p - £1.25 for regular-ish sliced white stuff*. The average in 2008? £1.17 - it's actually getting cheaper.
Who shops in Aldi and Lidl?
About 13%. Throw in the other budget operators like Iceland and the Co-op (and there are plenty of smaller regional ones) and you're not far off 1 in 4 people.
Not much cheaper? I've only been twice, one was last year to see what the fuss was about. A range of vegetables were 30% cheaper than I was used to paying - that's significant. And the point is that the big four have been lowering their prices to forestall loss of market share. (Average supermarket margins btw are about 2-3%).
I could be wrong, but it has increased everywhere. What has drove prices up has been most new builds becoming student housing as well as supply and demand. Most new builds near me are student housing only.
There are regions where prices stagnated or even fell: the NW, SW, Wales and NI. London has done well, and the big cities have done ok. Successful university cities have done well. But many middling cities and towns (ie the majority) have had quite a hard time of it and as a result accommodation prices to buy or rent have often fallen, either relatively or even absolutely.
I'll reiterate: everyone has a personal level of inflation - so your individual experience may be different. But on the whole, your food has become cheaper and your tax-free income has (barring catastophes) gone up.