Here are some relevant links that you may find useful:

Sunroofs
+ Webasto

Car Alarms
+ Sigma
+ VSIB

Car Stereo
+ Pioneer

Central Locking
+ PCA

Cruise Control
+ -

Electric Windows
+ PCA

Motability
+ Autochair
+ ELAP
+ Jeff Gosling
+ Brig-ayd
+ Cowal Mobility Products

Satellite Navigation
+ Panasonic
+ Pioneer

Towbars
+ Witter