1996 Polo Glow Plug light flashing

[stukinalift]

Hi all... really hope you can help me.

I have a VW Polo 1996 straight diesel 1.9 5 door.

Yesterday when leaving work I noticed that my Glow Plug Light flashed
for about 30 seconds after starting my car... I left it at that and
was going take it to a mechanic today.

This morning the car wouldn't start and the glow plug light was
flashing.
The engine was turning OK but white smoke was coming from the exhaust.

I when to my mechanic and he came to look at it.. he reckoned it was
the glow plugs.
I got my meter and check to see if the bus bar at the front of the
engine block (feeding the glow plugs) and found it wasn't getting 12v.

So we both had a fiddle to see if there were any broken wires or the
fuse etc..

He unplugged a relay with num 177 on it and the glow plug light did
not come on when this was plugged out.
He put it back in and the car started 1st time... waa laa.. we thought
that was it sorted.

Half an hour later i tried to start it but again it wouldn't start...
i tried doing what he did but to no avail.

Does anyone have any idea what it could be?... is it this relay... if
so where can I get one?

Thanks loads,
Shay