The lovely Maria from http://www.mynwoodcatjackets.com/ made it for me straightaway. I had a reflector strip put on it at the same time, it looks fab.
On her website, Maria provides detailed instructions on how to get a cat used to wearing a jacket. Wash puts up with most things, so we aren't anticipating major problems, but we're following Maria's recommendations anyway.
So far he's sniffed the jacket. I used it to stroke him, this is getting his scent on it too. I've fed him treats from it. I've laid it on the rug and put him on it. I've closed and opened the Velcro next to him (he's very sensitive to unexpected noise of any sort). And I've opened it, laid it on his back, and fed him treats and given him cuddles. That happened over the course of this morning.
He doesn't seem that bothered by it, so I put it on him did up the tummy strap lightly, and fussed him. Then I took it off.
The next step will be to put it on, do it up and see what he does. If he doesn't go mad, I'll take him outside and sit him on my knee. As recommended, I want hi to associate having the jacket on with the thing he wants most - going outside.
We'll see. Don't want to rush it. Well, I do want to rush it, but I'll try not to.