Hmmm, Just_Me you wax idea inspired me, so along with Brass Scorpion's advice I've improvised my solution:
Thick pin wire, like as thick as the sculpted joints pivot point on the Servo Arms, and a big ol' ball of Blu-Tack!
Drilled the pivot points out, entirely, and drilled a deep hole into the pack.
Then used the think wire to replace the sculpted detail, cut it to length, and filed it down to a flat edge...theoretically, you'll never know the difference! Then use the Blu-Tack (instead of wax, as I don't have any) to brace it all while the Araldite Rapid does its thing (fixing like super-glue and gap-filling like Green Stuff).
Presto! It's not perfect, but at least it looks like they'll stick this way!
I got the largest arm stuck this morning, and all the pin holes drilled ready, but then the snow failed me and I had to come to work
I'll try to get it finished off tonight.
For the record I think it's absolutely shocking that GW put this kit on sale as-is!
The Cannon took a fair amount of dremell work and gap filling out of the box, and the Techmarine is neigh on impossible.
Thanks for the help guys, wish me luck for later!