I lived in the UK and moved to the US to be with my husband.
In the UK, biggest problem is costs. It's getting expensive there. Petrol is expensive, groceries are expensive.
Pros are, healthcare is free. Con is that because it's free and everyone wants to use it, its quality has been getting depleted.
So advice: be stringent on saving up for retirement. If you run out of money and can't afford a good carehome, you go to the mercy of the NHS hospitals and the councils...it's not a good position. Another tip, network. It's hard to be alone in England.
Another tip: southeast England is where I came from. It's expensive as heck, but it was far more beautiful than London. London is smelly and cramped. I lived in Luton for a bit which is 20 minutes by train from London and it smelled just as bad.
Another tip: the weather is sometimes bad, you just have to learn to make a cosy environment for those times, i.e. fireplace, crumpets and toasting fork and jar of jam = cosy.
Another tip: don't be afraid to try british cuisine. It's considered strange to others but it is good such as toad in the hole, suet pudding, rock cakes, eve's pudding, yorkshire puddings, bakewell tart etc.