I have a similar problem as your Dad keeping my body warm and also hip pain when sleeping, since my early 50's. I have developed a moderately sucessful solution for my particular problems. Some of the things I do are:

* Switched my bedding to down. I use a down comforter & pillows instead of other bedding. It is light weight but insulates far better other products.
* Keep digest tract, large intestine, and colon clear at night. Use a heavy fiber such as Meta Mucil 4-in-1 to help with digestion and gas, use a mild laxative or stool softner with the fiber treatment if necessary. My leg pain reduced by 90 per cent after I improved my digestion and excretion.
* Exercise daily, especially lower trunk & pelvis area if possible. Jane Fonda has a wonderful senior workout CD.
* You should actually use light weight socks for sleeping not wool, use a good hand cream on you feet before putting the socks on. It helps the circulation.
* I use Arthritis Strength Tylonol and diclofenac for joint swelling and pain. I also have allergies, so I take over the counter antihistamines which help with sleep.
* Wear long underwear in winter. I wear leggings in summer under pajamas. I enjoy sleeping in air conditioning, but it activates my arthritis. My body temperature averages under 97 degrees so I have to work to keep my body warm. I live in a warm climate, but I enjoy my visits to MN in the winter when I visit the Mayo Clinic. I'm a cold weather lover living in the Appalachian Mountains over 18 years. Therefore, I do use long underwear under dresses, while sleeping, and out for a walk in cold climates. Hope everyone manages their symptoms!