So we went to the main Yamaha dealer in town where to our surprise, the lovely men there were only too pleased to help us out and sort two manky and by now exceptionally filthy Chinese scooters.
They very quickly established that the main head gasket was at fault and that the exhaust was loose and full of black oil - hence the mega smoking and loud banging. The cereal packet paper gaskets caught fire when I was riding it this morning too, so that didn't help on the smoke front.
So they changed all of that, replaced the seals, bought us tea, chatted to us about bikes, London, practised their English on us, introduced us to their families, produced some puppies ( called Lucky and Arsey) to amuse us, and then proceeded to go through both bikes looking for anything that needed doing, and doing it.
And all the time they kept giving us tea, and then lunch.
We spent about 4 hours with them and they were great, and the bill when it came was just £130.00 - £15.00 of which was the entire labour charge. Lovely people, and really cool. Thanks chaps!
So it looks like we'll be underway again tomorrow. We decided to stay here another night which was a good call as its tipped it down all afternoon - big fat horrible rain which would have drenched us and we'd have had to find another place to stay anyway, so we decided it was best to stay put and set off early in the morning.