MPG drop

[PieEater]

One thing I forgot to add into my original post which may or may not be connected is that tickover seems to have dropped down to below 1000 revs. Would this be as a result of carb balance or ignition advancer? I will re-adjust it but is this another symtom of low MPG?

Carbs are usually balanced with a raised tickover so it's possible that whoever balanced your carbs for you reset the tickover lower than it should be when they'd finished doing the balancing.