if you enter United Molasses Menstrie into Google or Menstrie into Flickr you will find quite a few photos, Blue 27, Railfreight grey 26s, LL 37 split headcode. There is a photo in the results with 4 tanks (Class 26 hauled), so you'll be all set.
Hope this helps
Thanks very much, chaps. It looks like in the 80s they were mainly 'plain rust' in appearance with TOPS numbering and 'caib' or similar branding, however I do have a BR Blue 27 and Railfreight Red Stripe 26, both of which should look the part hauling these.