Hi , Minic.
There are rudimentary pitches marked out in TR, 'tho few people pay any attention to them! A lot depends upon when you plan to arrive - by Thursday night you should have no trouble at all, by Friday night things start to get a tad busy, by Saturday morning a toilet tent is about all you can expect to erect !
Don't panic - there's always somewhere to doss down, even if you have a tree growing through the gazebo ! Plus - if you have a hot tub, you will find lots of people prepared to make room for you !