It's an interesting question, Sharen (for which I don't have an immediate answer).
But I notice you work in Medical Physics; don't (can't) you calibrate most of your test equipment yourselves, then?
Also, I would be selective about which items I would present to any specialist calibration company. Some of the modern kit can only be calibrated by the manufacturer, I would have thought. And most of the simple stuff (run of the mill multimeters and what-have-you) should not need a specialist (or may be done in-house as I have hinted at above).
As I have mentioned on here in the past. I believe that equipment should only need re-calibrating once it has proved to be "out of cal": Periodic calibration checks should be part of the PM of each item (annually, perhaps). Otherwise it is just (another) waste of money - or conversely, money for old rope for the service provider. Not to mention, of course, the length of time the kit itself is away being calibrated (and therefore unavailable for use) - even if being (expensively) addressed on site.
