I'm on my first R1150 GSA and it needs work. A fellow Maidstone Tosser gave me the details of a geezer in Pembury, who's an ex-dealer service technician and knows his onions. He'll be working on my bike the week after next.
Jimbogs1200 found Coopers TW to be competitive for his last service on a 12GS.
But to be honest if you want a BMW dealer then they are the only game in town. Otherwise you will have to ride up to Vines Caterham or down to Brighton.
From my experience Coopers have always done a good job for me.
Coopers in Tunbridge Wells have always done alright for me (in the end).
Brian Giles - BGM - is the guy in Pembury. Used to be a BMW mechanic, think he went solo when the previous dealer in Tunbridge Wells closed. He's very good!