For a budget (but quality) SIM don't rule out Alpkit - I've got an Airo 120. Bought it for lightweight backpacking but it's comfortable enough that I use it for 'normal' camping too. I'm looking at getting a Dirtbag or Dozer for the missus next year.
Only issue is stock - Alpkit seem to get caught out by rave reviews leading to runs on their gear.
Amazing family weekend with old steam engines, classic car displays, market stalls, and full catering and bar. And camping on site - Save £25 by booking in advance.