Hi Jamie
Your location makes this an easier question to answer.
HydraMaster
They are probably the number one UK T/M and have an extensive range. and superb customer support. Their new entry level Boxxer 318 has been very well received and, I am told, "punches above it's weight". They are, I would guess, a good couple of hours away from you, so not too far. It takes me 4 hours from the B'ham area.
I'm guessing on the prices as they are not published, but perhaps £10k to £11k fitted for the 318, rising to really big money for the higher spec machines. These prices are affected by the £/$ rate. Solution UK, who share the same address as HM, are about to announce their new UK built entry level TM which will be, I believe, in the £8k ball park.
Prochem and Alltec also have superb reputations for their products and support, but then you've got the servicing issue to consider with the miles apart.
Chemspec and Restormate (John Kelly) are also worth considering, but are moving further away from you. If you are handy with a spanner, it's less of an issue. Ashby's are new to T/M's so are an unknown quantity, although their range is highly regarded in Australia and elsewhere.
There are a few others around, but some of the feedback hasn't been generally favourable.
Before you buy, you need to define exactly what you want the T/M for. For example, a typical residential will typically be used at about 100ft hose run and light to moderate soiling levels. Many commercial jobs could be at 300, 400 or 500ft long hose runs with very high soiling levels so need a much more powerful machine.
Will your van be suitable? Weight is a major factor and regardless of kit, have a chat with Dave Ingram who has a lot of real world experience in this area. I believe that both Hydramaster and Alltec are able to offer very competitive van/TM packages, the van portion being better than through regular channels. Others may do the same thing.
You;ll probably have some sleepless nights to come over your decisions to be made
Safe and happy cleaning
Ken