Great news - Ambis Engineering are back. They supply an extremely useful range of bits and pieces for wagons. See MRJ 207 for more details.
The contact address is Ambis Engineering Products, 27 Stanhope Gardens, Ilford, Essex, IG1 3LQ. Strictly mail order only.
The 7mm scale products can also be had from Hobby Holidays. However, the products don't seem to show on the Hobby Holidays website yet.
