We have an above ground pool up all summer every year, not in the UK so can't comment on whether it's worth it weather wise, but definitely worth it in terms of fun v effort.
The ground needs to be level. Once the pool is up, filled and the filter connected you need to tests the water PH with a dip stick. Then add chemicals to increase/decrease the PH to the right level. That's a really quick job tbh, but it's the most important. Then you 'shock' it with one large dose of chlorine, leave for at least 8 hours, then you're good to use it assuming all is correct when you test it again before use. As long as you know how much water is in your pool, the chemical dosing is really straightforward.
You'll need a floating container for your chlorine tablets to maintain levels, you just put the right number in and put it in the pool. Test daily (1 minute job) and keep levels correct, topping up tablets as needed.
The filter will need running for the right amount of time each day (depending on pool size) and if they're paper filters, will need changing regularly. A whizz round the pool with a net is the only other thing you need to do.
It wont end up muddy, that's what the filter's for. Ours stays perfect for months with just a few minutes of attention each day.