Prickly problem!

I rescued this cactus last year when I helped clear an old lady's flat. I'm not very good with cactus so it was shoved out of sight at the end of a windowsill behind a cupboard. Despite being neglected it has decided to flower - maybe the spiders have been looking after it!!

Any advice on future care would be much appreciated.



sorry I'm late in posting but had trouble with PC last night.