Marty,
VAGCOM is software run on a laptop and it plugs into your
ODB port in the car.
You then do runs in your car in 3rd or 4th gear (2000 revs to redline) and it logs data, depending on what you have set to record.
This helps to determine if you car is running right (for example if you have a map you have not set you levels to aggressive and as a result have timing pull which is bad for the ECU). Various other data can be collected and analysed as well.
Furthermore you can use it to 'customise' some of your car settings. Such as switch on/off 'coming home' lights and many more.
You just need to buy the appropriate cable and software - more details at -
http://www.vagcom.co.uk/
Furthermore, if you want customise your map REVO do an SPS (Select Plus Switch) that plugs into the
ODB port and you can choose I think 1 of 3 maps. Usually STOCK and 2 custom one. Probably good for track days as you could increase the Boost for example
Back to your original question. There are many companies on here that allow you to order the parts via website (check the sponsors section on this forum).
Popular ones are Monster Motorsport (Nottingham), JKM (Portsmouth), Awesome GTI (Manchester), JBS (Chesterfield) to name a few.
Not familiar with those in Scotland.
However, with the others they would happily hold all items for you on order and fit. I guess Awesome are the closest but still a trek.
Good luck and keep us informed of your progress.
Any other questions just shout