I managed to break one of the cups off at the bracket, then I couldn't get the revolving bit to come off the pivot and bearing. I ended up drilling a hole through the centre cover and trying to gradually tap the bearing surround out of the housing, but then the pivot on top of the sensor (bearing centre) snapped.
I did eventually manage to get the bearing out, only to find the bearing would turn a few degrees back and forth, before jamming solid. Nothing I did would free the bearing, so despite it looking fine and feeling smooth over the few degrees I could manage to turn it, I ordered a replacement and hoped I could repair the damaged plastic parts. http://www.ebrbearings.co.uk/ was the cheapest source I could find for the replacement at £4.44 delivered - search for the 'MR1052Z'.
The centre of the pivot is hallow, so I managed to refix that in place using a steel pin down the centre and some Araldite. I also managed to refix the damaged cup in place again with Araldite, but reinforced by melting a paper staple into the plastic once the Araldite had set. To keep it reasnably balanced, I did similar to the other two cups - with some more Araldite over the top to prevent the steel staples rusting. I then used more Araldite to fill the hole in the top I had drilled in my attemps to release the bearing, to prevent water getting in.
The bearing, both inner and outer was a very tight fit. In the middle of all this my outdoor sensors stopped transmitting, which I found was due to the batteries being almost flat.
All now working again
