Took Friday afternon off work so would have more time to sort out the problems with the car. Still couldn't find any sign of fuel leaks, so turned my attention again to the carbs.
Turns out that the choke on the aft carb unit has become a bit tempermental and was sticking open. Combined with the float jet issue, it looks like this was the cause of the 10mpg fuel consumption.... The choke had been fine when the carbs were adjusted the previous weekend, so must have stuck again since - this time though I greased all the carb linkages / spindles etc so that both chokes move smoothly now.
Reset the mixture mainly on the at one, but the forward one also responded to a slight tweak, just using the lifting the carb pistons method (need to look at the plugs to check but haven't had time) & adjusted the idle screws. Now the engine idles very smoothly (also picks up without hesitation), and at the correct speed rather than a fast idle, which it hasn't done for as long as I can remember (always thought it was due to the D cam & that they were all like that).
Before it got dark, I also took the opportunity to redo the rear silencer hanger, which I had bodged previously with some jubilee clips. However when the exhaust is raised to the correct height, the centre silencer hits the new rear footwells (the old ones had been 'adjusted' with a BFH but I' mnot prepared to do that to these new panels). A quickly made extension piece fore the rear strap was made from a cut down Halfords exhaust bracket & it will do for the time being until I re-hang & re-route the exhaust properly.
At the end of all this, the car was running very nicely & the exhaust was quiet again as it wasn't hitting everywhere so I decided to use the Amazon to transport my gf & I to a weekend of sailing (just the other side of Poole) rather than taking her VW Lupo. I am pleased to report that the Amazon performed very well, with plenty of 'go' at motorway speeds and over 211 miles used just 34.5 litres of fuel (about 28mpg).
A big thanks again to all for advice etc.
