After checking through the kit (with help from Handy Andy) it turns out several parts were missing.
Interestingly they were the longest parts, which you think would be hard to lose...
There's a happy end to the story though. Handy Andy has lived up to his word above. Even though he didn't supply the kit to me, and it's been sat around for a year or so, Handy Andy has gone well out of his way to help me out.
He supplied the missing parts free of charge, and even threw in a fully welded front frame (as the kit was originally supplied before he started welding them up)
Many thanks for the top class service Andy!