Magpies - what to do?

Our problem is jackdaws. This year, they are hell bent on building their labrynthine nest under our solar panels. There are plenty of other places nearby they could go, but we really don't want them damaging the cabling to the panels with their beaks, ever-larger twigs, sticks, lumps of sheep's wool, old socks, feathers, etc. etc.

So, we put up my scaffolding and are clearing the nest out twice a day in the hope that they will get the message and give up. So far, they haven't. They just grumpily go off and find some more twigs and come back and shove them under with renewed enthusiasm.

The solar panel installers can erect some sort of guard around the whole lot, but it is expensive and has basic design flaws (can be removed by determined birds, and if they make a hole in it and shove nestbuilding stuff under, you cannot get at it to remove the nest!).

If anyone knows how long we will have to keep up this battle, or if there is a more effective deterrent, I'd be very glad to hear of it.