In England and Wales, wild camping is not actually permitted and you need the landowners permission to do so. However, this is not always practical when out walking and sometimes after a long day’s walk and the daylight is going, you just need to pitch a tent for the night. When doing so, on packing up, you should remove all trace that you have camped ensuring you take all pegs and litter with you. DO NOT LIGHT FIRES!
Toilets. When needing the toilet outdoors, make sure that you are at least 15m away from any water course and ideally, you will have a trowel (foldable trowels are available at most good outdoor stores) to bury any human waste a few inches deep and replacing any turf.
In Scotland, Wild Camping became legal in 2003 with the general rule being that a tent is for 1 or 2 people and only for one or two nights in any one place, being considerate to landowners. You can get further information at: http://www.outdooraccess-scotland.com
The Lake District allows Wild Camping above 450m with similar rules to Scotland.