Didn't get to Swinley, what with rugby and rain, so decided on a spell on the rollers (Kreitlers I brought back from the US but now available here).
Son2 (10) is a bike handling God, and picked it up in no time. This on his 24" MTB with Schwalbe half road, half trail tyres. Son1 (13) had a harder time on the road bike - likes to coast too much, but was OK when switched to fixed gear.
Rollers really show up technique - imagine riding for 30 min and never straying from a 15" path. Got to pedal smoothly and because mine have no flywheel, there is no coasting (hence fixed is easier). Vastly more fun that a turbo trainer.
Anyway Son1 is now up for some longer session to improve his track fitness. So a good result - teaching my sons to ride a bike again!