How about getting an ice pack thing which doesn't get wet on the outside, have in in the freezer in the day then put in in a hot water bottle cover or similar for night time, say rest your feet on it?
You can also get cooling sprays or get a nice moisturiser in a spray, I have a nice Simple Baby Body Lotion one, keep in in the fridge and spray overnight if needed so you get lovely soft skin as well.
Cooling gel eye masks are good, again you can put them in the fridge or freezer.
I find having long hair makes my neck worse so try and keep it up with a hairband i can tuck the rest of my hair into so no uncomfortable clips to lie on.
The cool sheets you can get (2 for 99p in Boots for their own brand) are also nice on the back of your neck).