Well since filling the tank we did a load of round town, bypass driving, stop start traffic, picked up a load of bags of gravel and did some shopping, also gave it a good clear out at speed, well that tank soon went. Filled back up Sunday eve, 11.8mpg averaged over that tank.
Today involved an early start for a day out, mainly motorway/dual carriageway with some 50mph road work sections, no hard accelerating and even behaving through a couple of tunnels (difficult to not floor it) not much stop start..... re fuelled it as got near home.
21.4 mpg average out of the old spirit burner. Quite happy with that. Mid range flat spot has gone, 65mph is around 2100rpm and will pull well from that without kicking the box down.
Fueling is definitely sorted now.
Have gained an exhaust drone at around 50mph and doesn't pop on overrun when hot anymore