Affordability and prices are very subjective. Whether you think it expensive compared to the UK is likely to depend on your income back home and also your buying behavior back home and the type of stores you frequent.

For information ..the supermarkets ..the one opposite Parque Santiago 3 and the one at Santiago 4 I enjoyed looking in but thought most of the stuff was horrendously expensive compared to the Uk

The Mercadona chain seems to be cheaper and thats where we food shopped ourselves.