I've booked Days hotel - walking distance to casino and nice and cheap.
I have also done this, had done so already tbh as was going to come and support/play local game if I was not picked.
Have stayed there before nice enough Hotel, has a bar etc, and the cafe between it and the casino is the nuts for getting fried breakfast. There is also a car park next door for I think £5/day or it is within walking distance of the casino if you don't mind leaving your car there.
http://www.dayshotel-luton.com/Price is going up though I got it for less than £40 per night. If you want to use this one book now imo as a lot of other teams will use it I would think.