No lights on Potterton Suprima 30

[LukeMc84]

I have a Potterton Suprima 30 connected to a boilermate II, they are about 11 years old and today I had no hot water. The boiler isolation fuse is fine and there is electricity leaving the isolation box. There are no LEDs illuminated on the boiler and I tested the 'mains' in to find no supply voltage. I am confused as to why the leads leaving the isolator are black/red and the one labelled 'mains' into the boiler PCB are brown/blue. This aside, all I have changed between having water yesterday and non today was the thermostat temperature (down to 0), which seems an unlikely cause as the boilermate store temperature and boiler setting are both still at max. I have put it back up now anyway.
Any ideas what might have caused the failure in boiler power?

 

[GavThePlumber]

I am confused as to why the leads leaving the isolator are black/red and the one labelled 'mains' into the boiler PCB are brown/blue.

 

[GavThePlumber]

What fuse was in the FCU?

 

[LukeMc84]

13A

I get what the colours mean, but the wire from the FCU must connected to a secondary place that I can't locate if a newer wire then leads into the PCB. I was just trying to trace the drop in V from the FCU is all.

 

[LukeMc84]

Job done, thanks.