In the UK the rules around wild camping is that it’s generally not something that is actively encouraged and their are local bylaws in different towns where you can or can’t park overnight.
Their are numerous websites dedicated to wild camping which are worth a read.
The important thing to consider is if you do want to wild camp need to look at where you are going to do this and who it could potentially upset.
If you are parking in a built up suburb of town try to park along side a wall not directly opposite a house. All it takes is a quick phone call from the homeowner to have a knock on your van door.
The other consideration is to park up late in the evening get your bed ready and sorted out in another place so all you need to do is arrive and pull the curtains and not have the lights on for an extended period of time.
Need to remember you are just sleeping at the chosen location don’t go their and start cooking and having all the lights on. This will draw attention to you and your van and have a knock on the door maybe by a local or the police.
Their are other types of wild camping that you can consider for example some pubs advertise park ups some charge a small fee or if you have dinner with them as payment. It’s cheaper than going to a campsite and if you planning to go at the last minute.