An update on the first full tank through after the work.
The fuel light clicked on a little early, with 1/8 of the tank remaining, and I filled up shortly afterwards.
Full brim to the top was just under 63 litres. Miles driven was 566 so I reckon that's pretty much between 40 and 41 mpg. Onboard computer showed 44.2 mpg.
The miles were a pretty even split over the last fortnight, and quite typical for me. A mix of short cold trips - 6 miles to work, sometimes popping out for 2-3 miles at lunch, and 6 miles back, and some similar evening journeys.
Then every fortnight a blast down the A12, M25, M23 and A23 from Ipswich to Brighton and back.
Town driving seems to average around 30 to 33 mpg. Motorway averages between 43 to 50 mpg, depending on what your interpretation of the speed limit is.
Good job all around. I must add that the 6th gear does now keep pulling and pulling and pulling...