Foot problems can be quite serious for diabetics as you seem to be aware. This month's newsletter from this site carries an article on foot care which suggests some orthopedic solutions to ensure footwear is comfortable and providing support to reduce this risk. Can anyone supply a link to this article since I cannot find it referenced on the main home page?
It may be as simple as cutting clearance holes in insoles to allow the skin to breathe, which solved one of my problems. Is the skin area weight bearing when you walk or stand? have you tried different sock materials such as wool instead of polyester? cotton? slippers when 'off duty'?
My GP surgery does not have any expertise on foot care, and I had to get a prescription issued to get an appointment at the local hospital orthopedic unit who are actually a private clinic that assists the NHS. There may be private chiropodists etc in your area that could provide consultancy,