Your friends best option would be the British Rabbit Council -
http://www.thebrc.org/ they govern rabbit breeding in the UK and set standards/put on shows. A rabbit show would be a good way to make local connections.
Velveteens aren't, as far as I'm aware, a recognised breed but it's likely that some people that do breed them have connections with the BRC.
The main issue with velveteens is that rex rabbits have very thin fur on the bottom of their feet which makes them prone to sore hocks (sores on the bottom of the feet) as rabbit have no pads. When the rex style fur is mixed with the added weight of an English lop sized rabbit is makes the problem even more of an issue. It maybe something breeds are working on.
Hope that helps