So this whole post may seem a little stupid to some people on here but oh well, you don't learn if you don't ask right?

Basically for the last few months I have been teaching myself 3D design and in my opinions i'm getting pretty damn good! Lol...

I understand quite a bit about aerodynamics and things, and my favourite thing to model is cars. Modelling a car from scratch, customising real-world cars, you name it I love it lol...

A few of my friends have seen my designs and have liked them that much that I've been asked about designing custom body kits and things like that. Now smaller pieces like dash trims and door handles I could obviously print at home if I had a 3D printer, but was stumped when it came to large objects such as bumpers or spoilers.

So my first question is:
Does the strength of the composite plastic that printers use vary? As in can you get stronger/weaker plastics or is it all pretty much the same stuff...

Second question:
Following the first question (thinking purely in terms of strength of material, excluding fitting issues and smoothing errors in design process) would it be better to treat the printed design only as a mould or in theory would the material be suitable for things like car bumpers?

Third question:
Would there be businesses capable of printing large items such as bumpers, or would larger items have to be printed in sections? (I live in the UK so if people can recommend business that could I would be extremely appreciative, but any advice would be appreciated)

I will leave it there for now, I'm sure I will have a few more questions but these are the main issues that I can think of right now

Thanks in advance