About 25 years ago I restored a 1927 Morris Oxford. All the Bakelite on the wheel had disappeared. I recoated the wheel using fiberglass resin coloured with black oxide cement colouring. I know this sounds odd but it worked and is still perfect today. You have to build up the coats and rotate the wheel as it dries so it doesn't sag, then wet rub and buff afterwards. You shouldn't use too much colouring, but build it up with several coats. I have done this on two vintage cars with great success. I too have to repair my Healey BN4 steering wheel. I'll fill the cracks first with an epoxy, possibly coloured black, sand, then coat the wheel with a few layers of the resin mixture then wet rub and buff. Don't know if it will work, but as I said, I did it 25 years ago and my wheel is still excellent. Good luck.
Matthew