Glow plug relay fault?

[zaskar]

2000 (x) 1.9d Romahome Duo / Berlingo

For some time now, the glow plug relay (I think) has been messing about. The light on the dash is staying on faaaaaaaaar longer than it should so I've got in the habit of just waiting 15 seconds and then firing her up first time, every time.

Tonight, came to fire her up, turned the key and the glow plug light lit up for one second and then went out with a click. No way would she fire.
I've taken the relay box  off, ( nearside inner wing) got inside it and had a look. Nothing obvious at all but I'm thinking it to be the most likely cause. 
Going to have a ring round tomorrow morning (fun on  a Sunday!) but would appreciate it if you could confirm I'm on the right track?

Thanks guys.

UPDATE. I've just made a short jumper cable direct from battery to glow plug supply wire. 10 seconds and she fired up straight away. Wire got a tad warm of course so i removed it straight away. Least I've got a work around until I can find a new controller.