EDIT-------Looks like the additional info is not necessary, in the time its taken me to post this up there has been a flurry of activity and it looks like the competition has been won!.......................................................................
Pleased its not been identified yet, I thought it was just me who couldn't read the writing either side of the logo which when you zoom in looks to me like a knight off a chess board with a castle off a chess board above it, and its definitely blue.
The grill arrangement is quite distinctive, and theres plenty pics to choose from on the Kent and East Sussex Railway's Car Rallies Gallery linked in my original post.
Here's another starter for 10......
regards Neil