I think that you've have problems getting somewhere now. We booked somewhere for the Saturday night but we decided about a month ago to drive up on the Friday and stay an extra day. We rang everywhere and couldn't get in, or if we did find somewhere it was £200 for the night. We ended up booking into the Holiday Inn @ Swindon. Think its right on the M4 and it doesn't look too far away. Start ringing around asap if you can. Good luck
ohh - we are staying in a B&B in Lacock (http://www.oldrectorylacock.co.uk/) - we stay there every year for badminton - its lovely. Lacock usually fills up quite quickly for badminton though.