I hope I'm a fair person, so in the interests of balance, this post is about the things that are actually cheaper in the UK than in Spain. As Eggcup commented yesterday, potatoes and apples are certainly cheaper, and in the case of apples, English apples are the best there is. We've basically given up on trying to find a decent apple in Spain - we tend to stick with oranges, soft fruits such as peaches and nectarines, and melons and berries.
I do like Spanish potatoes, although they are more expensive, but what really annoys me is that they don't carry the brands on the packaging like they do in the UK. Last week I bought some Maris Pipers for chips, but it's a job to find a decent chipping potato in Spain. Even those marked 'para frier' don't always work well. Still, it's a good excuse to keep my husband away from the frying pan - he'd have chips every day if I allowed it.
Bananas are another fruit that's cheaper over here - probably because they have to be imported. That said, a lot of the bananas on the Spanish markets only come from the Canary Islands, so they should really be cheaper.
Moving away from fruit and vegetables, one thing that's considerably cheaper here is milk. At the moment, Morrisons are selling a 4 pint carton of milk for just 97p - that's way cheaper than the 1.65 Euro I pay for 1.5 litres in Spain. For the mathematically challenged - which includes me - 4 pints is more than two litres, so milk is around half the price in the UK.
Another thing I've noticed is that you don't get the supermarket price wars in Spain - most of the stuff is the same price to within a few cents, wherever you shop. In the UK, you can save a lot by being a Supermarket Tart and taking the best of the offers from each establishment. There are also lots of BOGOF offers - again, you don't really get those in Spain. In Morrisons last week, tinned plum tomatoes were actually Buy 1, get 2 free, so I stocked up on those. In Spain, I always cook with fresh tomatoes, but they're too expensive to do that here.
One thing about being in the UK for an extended stay is that I need to do more shopping, so I'm getting a true picture of food and household costs. I'm one of those people who treats shopping as a necessary evil rather than a leisure pursuit, so I don't usually see so much of the insides of English supermarkets. It's certainly an eye opener.