Thank you all for the advice.
Rich - Well, I'm always being told I'm stubborn! At last it might pay off!
Nemerobis - You're probably right, but I don't want to purchase & have to learn a third program just now. I have looked at Blender too - but another (difficult) learning curve.
Hellnbak - Good idea, I'll look for those programs. Personally, I like to read a manual read, hence going for the tutorial e-books. Cars are not exactly my passion but a great deal of my business is indirectly for Mercedes-Benz so it would be an advantage.
PS. looking forward to seeing the moon buggy!