The bores are nearly all the same, but no.1 has deeper scores than the rest.
I've not had a chance to check the pistons yet, but I'll get everything stripped down and takes some pictures.
I've got all the service details for the car and it shows it had a belt and tensioner change at 37,356 miles (09/10), not sure if that's when the dodgy seal was fitted?
What makes you think the rocker covers been off, is it the amount of sealant residue that's around the sealing faces of the cover?