not sure about the uk, but im in Ireland and use Modelbau Seidel in Germany. Not the easiest to navigate but with the help of google translate you can manage. Just search TRF201 on it and you get all the 201 parts.
I put in an order on Monday and had it on Friday last week. Cant complain with their service.
http://www.modellbau-seidel.de/