I just found out about E30 318iS competing in the BTCC in 1990 and 1991. Robin Brundle drove one in 1990 under the Techspeed banner and in 1991, Angus MacKay and Alistair Lyall raced under the R&D Motorsport banner.
If anyone has more information or better pics, please post them.
(http://i127.photobucket.com/albums/p152/birminghamsuperprix/1990_BSP_Rouse_Baird_PeterGillott.jpg)
(credit Peter Gillott)
(http://www.supertouring.co.uk/gallery/1990/baird_90.jpg) (http://www.supertouring.co.uk/gallery/1991/lyall_01.jpg)