I'm having some installed over the next few weeks. If memory serves me correctly you a few miles down the road from me. ( You delivered a Longines Legend Diver to me when I bought it off another member). Once they have been installed will let you know if they're any good.
The price is
£4000 installed. (remote)
I am also spending a further £1600 on a Comelit intercom which will work in conjunction with it.