Each of those manufacturers will have separate training courses. For example Hexis training is held in the Hexis HQ in Lichfield. The 3M training is usually held at William Smith (Supplier near Newcastle).
In terms of suppliers I use a variation of William Smith and Spandex UK who cover all the manufacturers you have mentioned. What I will say is do not just buy materials from what you have heard about them. I would say put in some market research and find out your favourite materials with hands on experience.
Also you need to factor in many things to unit rental such as overheads, heating (beyond important!), cleanliness… If the unit is cheap but you cannot control the temperature then I would not use it for vehicle wrapping, again with dust and dirt control. Companies pour money into having clean units to work in as dust underneath a wrap does not look good at all.
Just some things to look out for not trying to put you off. Hopefully it all works out nicely bud and you can get those Instagram fame corner shots haha. :thumbup2: