Thanks, the dish is at the back of the house, south, south west side, and abut 4' off the ground.
I have used those brackets high up on 1m dishes with no issues. They are made by Vanjak Rigging Supplies in NI, and are very strong. It is attached to the wall by four 10mm dia. "Thunder Bolts" no plugs or sleeves, very strong.
The slim Alps lnbs are as good as any average lnb, the one on 16e on centre is just wedged in there, held in place by it's neighbours.