The problem is the kit seems to be of one of the three "tarmac special" cars built for 1979 (although, seeing the last photo, the front spoiler seems to be that of a normal works car).
Two were the striped Monte cars mentioned earlier and the third was used by Brookes on the 79 Circuit of Ireland and Manx in Andrews colours (and carried two different registration numbers in its short life - TWC234R on the Circuit and GVX489T on the Manx, but the same car).
The 77 RAC cars were normal forest cars, not the lowered, changed wheelbase, ultra wide arched cars of this kit. So, sorry, it's totally wrong to depict it in BA colours.