I checked the hose again this morning and sure enough, sweating fluid still. Damn thing is like old dynamite sweating nitro! Here are some pics of the paintwork damage:
The hose is £30 from TPS. Vexing, but not the end of the world.
The reservoir however... £240!!!!
For that much I can buy a whole master cylinder and reservoir for a 4 or 6, so sod the '8 tax' unobtanium stuff - retrofit the cheap versions
Initial tinkering suggests a C5 RS5 setup will go in, and the bore is identical and the reservoir for that is about £35...