Mr Haynes tells me Skoda recommend loctite 270 on these bolts - which sells itself as a threadlock to use when you don't want to undo things later (incidentally I've found a cheap rip off version of it for £1.65 in toolstation under the brand name bondloc calling itself b270).

Is it really unremovable or just a case of a long breaker bar and some muscle?

it's better than he bolt working itself loose on the motorway, and it isn't unremovable

Dont cover the thing in it though LOL

Just a wee spot at the top of the thread will do