Hi Figo, only just came across this thread, so did you secure anything yet?
Even in better times Spain has never been anywhere close to UK in terms of achievable rental yields.
Couple of things to be aware of as you mentioned 1 bed flats for retired people:
(a) Sounds like you have a 25% deposit which is great but there's no BTL lender in UK who would lend against these type of properties.
(b) Even if you had the money to buy outright, there will generally be restrictive covenants that don't allow sub-letting, hence there's no legal scope for investor landlords.
There are lots of different ways to make money in the current UK market (or alternatively lose money I might add!). I source investment properties primarily in the midlands area and have contacts nationwide but wouldn't dream of flouting forum rules so wont post any contact info. If you want to drop me a pm I'll simply recommend you visit a specific property forum where the type of advice you seek is freely available via people from all types of backgrounds with a broad range of experience.