i belive its 18nm as change mine on 2.5tdi...it was printed on the end of the glow plug box so went with that...am sure someone will come along and correct my if wrong....not to bad a job bit fiddly tho...
Found it written on the box 10 secs after posting!
They need to be torque'd up to 15nm (as was written on the box).
The job is a pretty easy one for anyone attempting it, but is WAY easier if you remove the radiator and do a coolant flush at the same time! Will certainly be taking the radiator off again shortly when I come to do the injectors in a month or so.
Happy to report that was down on 2 glow plugs so the cold starting should be much improved now!