I do have quite a lot of identical hardware, with more to be added in the near future.
The part I don't understand is that no other project I attach to has this particular problem, it seems to me that they use the unique host host_cpid identifier but WCG does not? Seems strange to me.

That being said, when I return from my travels I will spend some time altering hostnames and purging/reinstalling boinc-client on the collective. If this fixes it, then there should be no problems moving forward, the identical hostname scenario is a leftover from the installation workflow that can be avoided in the future.