*Update*
I took the bike out for a test ride before our Alps trip in a few weeks yesterday.
In the end I went for some clearance Superstar 1500g wheels, Conti GP4000’s, light tubes and a 10 speed 11-32 XT cassette. This has shaved over 800 grams over what came fitted with 500g + off the back wheel.
The bike rode like I always thought a road bike should. Before it was nearly as much hard work as my lightweight MTB. Yesterday it felt really quick even though I had done 50 miles the day before off road.
A great upgrade for under £300 quid, roll on the Alps
And thanks for the input, even the ones I have ignored.