Overly legislated?...
If you are careful, the only real problem with what you suggest is the fire in a forest.
Free camping is easier in more remote places, you just need to use your nouse to stay clear of gateways etc (I regularly freecamp in a converted van) and don’t stay more than one night in one place. And of course, have consideration for the area you decide to stay in – don’t play loud music, which will draw attention to yourself AND may be disturbing to anyone in the vicinity; take all litter away with you; IF you make a fire, choose your location incredibly carefully, douse it out before going to sleep, and clear it away in the morning as much as possible.
Be really aware of rights of way and be vigilant for livestock – plenty of sheep and cattle in __them there hills__ so be sure you are not going to disturb them, or worse, scare them. Close all gates etc etc. Being anywhere near livestock does mean you’re more likely to be found and asked to move on by a farmer.
You probably don’t need to hear most of this as it’s mainly common sense – short answer: Yes it is possible to free-camp in the UK, though it is not encouraged, so use your head!
I have found Scotland is the easiest place to free camp in, England required more care and forethought, and I haven’t dared try it in Wales yet.
Good news is, you can’t be shot for trespassing, or rather, you can’t legally be shot for trespassing! Farmers, however, are absolutely allowed to shoot animals that worry their livestock – including dogs – and it wouldn’t be an idea to be mistaken as one!