For anyone who's's interested, just got back from weekend trip and noted following fuel consumption info:

24.8 MPG average

UK STi7 Prodrive Style
3K miles ish on the clock
mostly motorway driving
2 tanks of Optimax, 1 tank of Super Unleaded
130.65 litres total fuel used
713 miles total

 

I used more than 3 tanks at the weekend as well. I only covered about 420 miles though in total. Virtually no motorway driving at all

Thouroughly enjoyable, and the car feels a lot lot better now after having some real exercise!

John