Some of the fragments of the old belt are still there - I'll have a look.
I've also managed to find the part numbers from the receipt from the garage that replaced all the belts in July 2017. I've done 12000 miles since then so I wouldn't expect one to disintegrate. I don't suppose there's any point trying to get them replaced for free? The other belts are the same make so they don't fill me with confidence.
I'll take a look at the part numbers of the belts that are on there and try to work out which belt I need by process of elimination. Tbh, I might try my breakdown cover as I won't be around to fix the car over the next couple of days.
Thankfully we have two cars - so I can use that to get to work in the meantime, but having one off the road makes things a lot more difficult.