yep I wear nice fluffy socks too. I have a pair of Next ones that look like highland cattle.
Kaz did you know you shouldn't warm a bad back you should ice it. My osteopath lady says warming a bad back just further inflames the muscles, it feel nice at the time, but delays the healing. She had a client who just wasn't getting better then told her he had driven 40 miles with his heated seat on.
I use an ice block wrapped in a tea towel and sit against it for 15 mins when my back plays up