TDCI Heated Front Windscreen Fault

Hi All (again!)
Today's question is about electrikery on my 2010 110 XS Utility Wagon;
I've had the vehicle just over a year and about 5 months ago (when it was cold) I noticed the heated front windscreen had stopped working (it had worked when I first got the vehicle). After a bit of investigating I've discovered there are 2 relays which can go wrong: one costs £5 and the other £90!. I tried changing the cheap one and it seemed to work - for about a day. This led me to conclude it was the more expensive one so I tracked down one on eBay (guaranteed to work) and to make sure got another £5 one as well but nothing!!!! It still won't work but there is a 'clicking' sound from one of them when I press the button! Any advice at all would be helpful including a picture identifying what relay does what in the compartment under the seat!
Thanks in advance
TT

The grey one is a timer relay and needs an engine running signal from the instrument cluster, this is used to activate the timer relay when the heated screen switch is pressed. this relay then picks the yellow heated screen relay. Check your fuses and then the power and grounds to the relays, then the outputs and the continuity of the screen.

Thanks for that - which grey one do you mean as from memory I think there's 2?
Thanks
TT

I think it is the one nearest the front of the car, however if you remove the relay one of the connections in the plug should ground when the switch is pressed.