Agree with the comment on difficulty in sourcing UK rail items here, I have probably bought 98% of my gear either through ebay or Hattons, paints I buy from the model shop in Braemar close to Mittagong, www.highlandsnsw.com.au/allaboard/?. Keep a lookout on Vectis Auction site in the UK, I got a couple of WM kits a month or so back, they have a lot of speciality stuff on there. Not sure where you are but if you are after Mashima motors I have seen Berg's in Parramatta have a few different models listed.
Good luck
Kevin
Sydney