Just spoke to WMSS, the car is ready, has been road tested, and all is fine.
The corner of the radiator where a few drops were spotted seems to be ok now the car isn’t over-pressuring massively, but if I do notice any future coolant issues, I’ll remember to check there.
Cost appears to be £396, and seems to include a fair bit of stuff including new head bolts, various gaskets, thermostat etc. I’ll post more when I get the full breakdown, but it’s a price I can cope with.
Collection will be on Friday, so I’ll post more info when I get the car back.