Those are the two things that I only ever hear about when people talk about orienteering in UK... That doesn't sound like fun.
It's in abundance here. And tons of bramble in the forests. Although it was mostly deadfall yesterday. I think the further south you go the less you get it.
I do enjoy a bit of heather. But yesterday it was ridiculously high. The bracken aspect made for running later especially beneficial due to the elephant tracks.
You're right, however, it's not anything like New England or Wyoming where you can run 100% of the time.