Various suppliers have been very helpfull to me in putting the car together, and if you like the look of anything used then here are some links to make your search easier.
These are not in any order, just as I have used them. Roughly.

These guys are very helpfull, and noticeably less expensive than other makes. They supply brakes for endurance racing, so I assume they know what they are about. Also supply various other parts to build a competition car. The calipers are made by them, which is always good.

Well known purveyors of roll cages, also well known for not fitting and having appalling instructions. On the bright side, the cage is very substantial. One of my friends wants to paint the cage red oxide, like the forth road bridge.

Very knowledgeable suspension designers. They do not want to simply sell boxes, and when I ordered the front ARB they rang to ensure I knew what I was doing. They could not have been more helpfull.

Sean is a top man. Well known in the escort world, but makes good quality one off welded fabrications. My tank was exactly as designed. Very competitive pricing and good delivery

Faye used to drive a top fuel dragster, and absolutely amazed me when I went to see her with her knowledge of pipe fittings. Very easy to deal with and a mine of knowledge.

John is not just a circuit racing guru, which can be a problem with some BMW suppliers. He talked me through why we were having the spring rates we were having, what effect they would have and didn’t mind my constant questioning.
Prospect Auto Spares >
This is my local motor factor, but they sell parts all over the world from their website. Brian and the gang have a steady stream of local motorsport people so are quite used to bizarre requests.

Very helpfull company. Have a good range of equipment and fast RELIABLE delivery. I so wish every company understood this basic premise.
Vehicle Wiring Products
As the name suggests they Supply bits to help you wire the car. I have listed two companies here as no one supplier has all the little bits that you need.

ProfiCAD produce the software I used to draw all the electrical drawings. If you are used to systems that automatically produce schedules, and have built-in intelligence this will frustrate you. If you are not used to electrical drawings you will get on just fine with it. For personal use it is also free, which is a major bonus. I had a problem after an upgrade and they were very quick to respond.

Martin is a fellow BMW rally person, so a good source of help and advice. I bought my ECU from Martin.
Chipwizards
Wayne, generally known as Wayne the Brain, is a top man who has a very good and deserved reputation. His Web Page on the other hand is pants, and has nothing beyond an address. If you ring and leave a message he will get back to you, but he is very busy and it could be a couple of days. Don’t be put off by the Chip part of the title, he maps all motorsport ECUs and many OEM ECUs.
Work Phone 01706 651000