It depends where you go in the UK. I'd be amazed if you could find much litter around here in our small town (of fewer than 5000 people) because there's a full-time litter collector employed by the town council and volunteer teams who help out at weekends. There's actually very little for them to do because people see a clean town and keep it that way.
Even the nearest large town (Ipswich, pop.approx 135000) has hardly any litter because there are loads of wardens ready to hand out penalty notices to people who drop a fag end.
When I lived in Sheffield (back in the 1970s and 1980s) the litter situation in the city centre was appalling, with ankle-deep litter carpeting the Castle Market area on a Saturday afternoon. The attitude of young people towards litter was also terrible. (I taught teenagers, from 'nice' homes, who simply couldn't see anything wrong with dropping their crisp packets in the playground or in the school corridors. If you challenged them about it they'd simply say "That's what cleaners are for" and their parents would usually agree with them). I've not been to Sheffield very many times since I left there but it's clear that they've now started to get well on top of the litter problem and that young people's attitudes have been changed.
So, as I see it, things are now vastly better than they were a couple of decades ago.