Why do you need to use the turbo in the summer?
Programmable interval training.
Accurate power/training data.
Specific training (i.e. 30km hillclimbs) that can't be done in SW London (winter or summer).
Haven't got mine yet but it's looking like it'll have to go in the shed. It'll make too much noise for the downstairs neighbours if I do it inside.
But yes, the vast majority of my riding will be on the road, regardless of season. But I'll still want to do targeted training, or performance analysis, throughout the year.