Frying pan into the fire.

[Mark Hennessy]

...madness IMHO a PCV system that carbonises the backs of the inlet valves

It's not because of the PCV system as such - we know that cars have had PCV for decades - rather, it's the move to direct injection.

Older engines using port injection benefited from the petrol in the air/fuel mix cleaning the valves.

Some engines have both - the Ford 1.5 Ecoboost was one I read about a couple of years back - but it's hard to know whether the port injection works sufficiently often to help with this problem. Indeed, I don't think I discovered under what driving conditions port injection was used. I didn't end up buying one for various other reasons (but it was very nice to drive, like all petrol Fords that I've experienced).

Now that most engines use GDI, I guess we'll learn a lot more about how best to cope with this - walnut blasting sounds like fun! But I agree that long service intervals does not seem like a good plan for those of us who don't change their cars every 3 years when the PCP lease is up. Much as it goes against the grain, a huge number of people buy cars this way, and that's who the manufacturers cater for - that's just the economic reality, sadly...

Did the cold start give you cause for optimism?