The new heater matrix, ordered off ebay, means I can finish off the job from last weekend. Its a copper & brass replacement, supplied with some foam padding. It is a direct replacement for the original.

After I had split the heater assembly in half the other weekend it would seem that I have given it a bit of force I may have been able to extract the matrix without splitting the assembly and breaking all the clips. Luckily it would appear they had expected it to be split as there were holes and receivers next to the damaged clips, so I've used some self-tappers to put it all back together again.

The rest of the process is simple enough, put it back together in the reverse order it came out in. Simples.

Simple enough it was, and with only three bolts & two plugs left afterwards too. If I were to recommend anything to anyone else looking to replace the heater matix; try Radweld first.