Sorry I was working before so will elaborate a bit now.
So ! I think the U.K. deffo has its faults but I wouldn't say spain is any better tbh.
There are huge problems with housing obviously this depends on what area you would be planning on moving to but it is almost impossible anywhere that is touristy to find a reasonably priced rental and buying prices are sky high. I would have much better accommodation choices in the U.K. because I am from the north.
Driving since brexit you may need to look into if you would need to do a driving test in order to drive here because the rules seem to change constantly. I have recently bought a very average car for 20 thousand euros cars are so expensive here.
Anything to do with anything basically is hard work especially if you aren't fluent in Spanish. You end up having to pay people to do basic tasks for you and it's constant.
Taxes are in my opinion a lot worse than they are in the U.K. and the government can just embargo your bank account if you owe so much as a parking fine.
Healthcare is no better than the U.K. and I have found when anyone is admitted to hospital here it is the family who are expected to care for the patient for example wash them and feed them if necessary. As a foreigner you aren't always treated well or welcomed so probably need to get health insurance which costs hundreds a month.
Getting anything delivered is an absolute nightmare and the choice of things available is not as varied. Supermarkets for example don't have special offers and very rarely change their stock so it's all just a bit boring and no convenience. Customer service is really lacking and you are lucky to get a hola.
Moving here since brexit is not easy your finances are looked into because basically the main thing the government in Spain are interested in is extracting as much money from people as possible and this goes for Spanish citizens too. Being self employed is a nightmare you have to pay 300 and off euros a month just to be registered that's before you make a cent and that's not tax that's just to be registered it doesn't matter if you are a cleaner or a dentist you all pay the same it's such a stupid system,
Living anywhere that is considered a tourist destination is a nightmare in the summer. Nowhere to park, constant noise, everywhere is just full and the infrastructure can not cope. It's often over 40 degrees too. There is a severely water shortage in a lot of areas because no money has been put into to drainage.
I could go on and on.
I know this all sounds very negative I don't have an awful life here but I do think my standard of living and opportunities were far higher in the U.K. and honestly even though I'm contributing and doing my best I don't feel massively welcome by the locals and that's fair enough I suppose because the U.K. don't welcome immigrants either and that's what you would be don't fool yourself it's only the British who like to call us expats