Leyland, Scammell, AEC, albion, Dodge, and of course the massive diamond T used by the army as a tank transporter, not sure where that was built though, there was a three wheeled tractive unit known as the scarab, it was comonly in use at rail stations etc,
As said the 3 wheelers were Scammell Scarab's. They come out in several different versions and were known as 'mechanical horses'. They could spin round in their own length, making them very handy in confined yards. Put Scammell Scarab in google and you'll get loads of stuff, but heres a start. http://homepage.ntlworld.com/malcolm.ruscoe/me chanical%20horse.htm
The Diamond T heavy tractor was designed to a British Army requirement by the American Diamond T Corporation. Built from 1941-45, they adopted by the American Army after proving successful with the British army in the Middle East. They were used to tow multi-wheel trailers the America 40 or 45ton Rogers or a British equivalent built by Cranes. A powerful winch was fitted between the cab and body for the loading of disabled vehicles. Later versions were fitted with a open cab standardised on American vehicles. Over 6500 were built. They continued to serve with the British Army until the early 1970�s By which in 1956 had their 201bhp Hercules engines had been replaced by Rolls Royce F6FNL-134 diesel engines which not only increased there road speed but up rated their pulling capacity to 50ton. They also had a wood and canvas �shed� built over the ballast body for crew accommodation and stowage of equipment