I like Guy Martin. He's like a modern day Fred Dibnah in some respects. I agree he's a Marmite character, but his 'Speed' progs are good as are some of his other documentaries about how things were made. I think he's best left there. He's no Clarkson, for all his 'failings, Clarkson is much smarter and in-tune than Martin whose persona is more about wide eyed-boyish enthusiasm. He'd be bit shoot at Top Gear.
Frankly TG is a dog that's had its day. It should be put out of its misery and after a brief period of remembrance perhaps the Beeb could do as suggested up-thread and that's produce a program that is about the future of motoring and transport and what could be rather than dwelling on its past glories.
Cars have become ridiculous items, items of vanity. There needs to be a change of heart, not more of the same otherwise the 'Petrolhead' crash when it happens will be a major wreck.