UK touring - Do you need to book in advance?

Hi,

We have started planning our 2 week "big" summer holiday and are going to stay in the UK this year instead of our usual trip across the channel. We'll be going end of June, so out of school holiday time.

Can anyone advise me please - is it possible to tour around, doing a few nights here, a few nights there without booking in advance? Are pitches available in most places if you just turn up?

We haven't really decided exactly where to go (but are having fun looking!), but on the possible list is North Wales, Lake District, Northumberland coast and Scotland. The reason for asking is that we've never really tried it before, but have always struggled to get availability mid-September in Devon and Dorset, especially on club sites, and that's booking 2-3 months in advance. I'm not sure if that is particular to the location or time of year?

Any insights appreciated, TIA.