>>1582520You don't want to start going /out/ by going for multi day hikes and wild camping along the way.
Just go to the lake district. Book into a paid campsite and then go hiking in the surrounding area. Climb Scafell Pike while you are there. When you have done that and tested all your gear you can figure choose to do some other stuff.
Once you have done that then you can work your way upto other stuff. The Cape Wrath trail is a long distance walk in the Scotish highlands, you can go for a days without seeing another person.
>>1583952This is a very good point. The only real 'wilderness' in the UK is the Scottish highlands, and it is often cheaper to fly to Europe than it is to get to the highlands. For the same price as a train ticket to the highlands you can get a flight to the Carpathian mountains, and your living expenses will be cheaper while you are there.