I booked into Singleton Hotel, which says "Free Public Parking" nearby. It was dead cheap with decent reviews. I wanted something close to Casino, and it was the one of the closest with rooms available through booking.com. It will sleep up to three for £65 and includes full english. Reviews average 8 out of 10, but not great reviews.
I also reserved 2 Club Twins @£80, that look much nicer. Those are at the Grand Hotel with a few rooms left there. Not sure about parking..
The Alexander has two rooms left, with free public parking close by and is list as 1. mile from centre.
www.booking.com allows you to book without prepay (most of the time), still get a discount and no cancellation fee if you cancel 2 days in advance.