Your not a million miles from Leicester, if you want to pop over I have a box of several hundred O rings in a range of sizes, these kind of drain plugs normally have a rubber O ring which hardens and fails. Your welcome to grab a few of each size and take back to play if you want? I agree though PTFE is just as good and also the suggestion of KSeal is a good one. These radiators have a history of failure I am afraid although normally the top hose outlet or the overflow elbow goes first, Peter at Mulfab always recommends running the cars with KSeal added to the coolant as a safety thing. I am in all day if you want to pop over PM me and I will send address.
