A couple of things. Yes, black ones are harder to rehome. This applies to all dogs, not just greys, and even applies to cats too. Many people don't like black dogs, find them threatening, and there is also a great deal of superstition around them which seems to leave lingering doubts with people. 
We have two black ones who we love to bits, and I think no other colour shines so beautifully when their coats are in good nick. They gleam in the sun.
Viva, so sorry to hear you have been ill. As well as the Cinnamon Trust (excellent idea) why not contact the rescue you adopted through and see if any of their volunteers lives near you and would be willing to do a bit of extra walking or take yours out with theirs for a mini-playdate? Grunds love meeting up with other pointies and most greyhound owners I know seem to be happy to help out other pointy owners - seems we feel we are part of a special "club" if you know what I mean. If this was one of our adopters I would be mortified if I thought they couldn't contact the charity for help and a bit of support.
Coats - haven't bought from RGT so am disappointed to hear this. You would indeed think that the idea of selling more coats as winter approaches wouldn't come as a surprise. AK Creations are great, we've bought housecoats from them for ours. We got our outdoor coats from here - although it's in the USA, we found the service to be excellent, and it's nice to know it's supporting a rescue. GRWE also have an online shop which sells coats and accessories.
If we are talking shopping though, we need to mention - whisper - collar porn. 
Try Around the hounds or 2 Hounds for some luscious collar browsing. Apart from looking wonderful, we've bought collars and leads from both these companies, and I can say they are top quality and very comfortable for the dogs. The 2 Hounds velvet leashes are amazing, they are incredibly strong, machine washable and look wonderful day in day out.