There is loads to go through and i type slow, easiest to narrow things down a bit. A 400 burg will prob do 90mph+ and 70- 90mpg, a 650 115mph and 50-70mpg. I'm sure mpg can vary wildly depending on throttle, loads etc. Modern scooters have a relaxed feel, even flat out, so the 400 would be enough. Oil change intervals are short but they hold less so costs are similar. The internal belt will do very roughly 15000 miles for £100, tyres are £150 a pair and last forever. The 650 is expensive, the 400 cheap. A lot of maxi scooters are wide and heavy and have a semi cruiser riding position, a Yam tmax 500 is one of the best of the lot. If not bothered about ride outs with mates a Yam 250 xmax would be my choice for you, fine on the motorway and perfect off it.
