Update - a further 300 miles or so and no problems. 
Just back from a week of holiday in South Devon (UK) with plenty of gravel riding and no issues.
Video link below to some of the typical terrain covered:
I’m impressed with how they coped with the gravel and rocks - some of it was fairly ‘sharp’ including a particularly challenging downhill section. I’m a heavier rider so with 80psi rear and 75psi front on 28mm tyres on my road bike (Cannondale Synapse) I was definitely expecting a blowout at some point given the weather was hot so the ground was very dry. It wasn’t as if I was taking it super easy on some parts either.