Thanks for all the advice.
After the first failure I asked the electricians about changing to the Juice panels and they said that the panels they supplied differed in that they were 36v and therefore charged better in low light?? The Juice panels were also a different size so cosmetic touchups were going to be required so I stuck with the same panels. Clearly that's not an option again though!!
I haven't checked what regulator I have yet, but could this need changing if going to 12v panels which I think is what Juice are?
The panels do go onto the solid slightly curved surf