Saxabar, I've also been with Ian (last year). I took my 29 hardtail and I thought it was perfect, but I find it pretty good down hill on all but really technical downhill. Friends of mine have also been and used everything from Ian's hire bikes up to orange 5's, nobody has come back and said they felt they'd take the wrong bike.
I really enjoyed the week, by the time I got home I was the fittest I've ever been. As already mention Ian has put a lot of time I to his routes and each day is a bigger ride than the last. As I recall there are 5 days of riding, ride days 1,2,3 off day 4 and ride 5 and 6. I was knackered by day 3 and really enjoyed the day off, but was then flying days 4 and 5.
Beaches are good and yes it's hot