Not sure where you live, but Lecestershire OC seem quite active.
If you can get this link, it is a thing called Routegadget.
https://www.leioc.routegadget.co.uk/rg2/index.php#112 On the left should be a list of past events run by Lecestershire OC. If you recognise anywhere local to you, click on it and it should show a copy of the orienteering map, so you can get an idea of what they look like.
A lot of those areas are urban (olive green is out of bounds - often gardens).
Some are woodland. Confusingly, wooded areas are white and increasing shades of green. Yellow is open land.
The only Lecestershire OC area I have raced on is Irchester - it's on the old open cast ironstone quarries, and is hideously complicated.
I lost a lot of time on the first few controls till I got the hang of it, then it was fun...
In the less populated regions, we often run on open fells. Here's this year's LongO
https://www.bl.routegadget.co.uk/rg2/#143&course=2Courses ranged from 5k to 18k. NB orienteering courses are measured in a straight line, actual distance is likely to be at least 50% more.