Sounds like you need another question added to the famous PPQ form, Jim.
But what sort of kit are we talking about here? Surely the "answer" is to support it in-house (that is, yourselves).
And, if the kit needs special resources (as in the case of x-ray units and so forth), why not lobby the NHS to get its finger out and get engineering services properly structured on a Regional basis (with second-, and third-, line workshops, and specialist engineers travelling around; plus a central technical training school and all the rest).
I have never understood how (and why) such a large user of "high-tech" kit has managed to get away with not having a properly organised tech support structure.