The answer to the petrol smell was quite straightforward. There is an overflow pipe for when my carburettor gets a little over-enthusiastic and has excess petrol. This should normally be piped away and vented safely. At the moment this little pipe is broken off so John is going to re-instate it the way it should be.
The other problem is more worrying. I mentioned the rather high water consumption and John could find no leak in my coolant system. This means the water must be venting through my engine somewhere. This could be due to a damaged head gasket, cracked head, cracked block or cracked cylinder sleeve. None of which are trivial matters.
So, my engine is coming out and I will be spending quite a bit of time with John and the boys at Bewley Motors.
So, perhaps it was that bad after all!