Yes, it is getting more expensive and so it should be. The proportion of UK household expenditure which is accounted for by food (15% in 2007) has more than halved since 1957 when it was 33% and fallen by almost a quarter since 1987 when it was 19%.
Whilst UK total household expenditure and incomes have gone up in real terms over the last 10 years, expenditure on food has actually fallen in real terms over the same period. This is despite the fact that at the same time, domestically the amount of land allocated to farming in the UK has fallen by 0.8 million hectares over the same period and globally of the world population has increased by 800 million. It's only been the dynamics of the UK grocery market (not least the main groups' purchasing power) that has enabled prices to stay articificially low. Right now, as Callisto says, the inherently unstable food market has been exposed by a variety of global factors but principally increasing demand and fixed (or falling) supply. So prices have gone up and will at best, stay where they are.
We have become accustomed to unsustainably cheap food available when we want, where we want. Someone said, gosh a red pepper costs 89p now. So it bloody should. It's probably been flown in from Venezuela. Someone said meat is getting more expensive. Yes, well it costs $8 to produce $1 of beef, how is that sustainable in the long term? These sort of foods should be premium products, not part of our basic diet and we certainly shouldn't be whinging that they're getting more expensive.
Apologies, this is something of a rant. But frankly, I'm staggered that people are complaining about the cost of food over here when the WHO estimates that 1/3 of the world's population is well fed, 1/3 is underfed and 1/3 is starving, yes, actually starving, as in watching your child die from hunger in front of you (15 million children last year in fact). Just to give a little perspective here, but worth thinking about.