Yes it is legal!
The PCT has the right to procure individual contracts with suppliers of medical equipment, this enables the PCT to keep costs down.... Less staff training costs, less software to purchase as well as less cost in consumables at the patient end.
However, the PCT has to uphold an individual waiver system, that patients can use other available NHS equipment if they have good reason for doing so...
So in the case of the Glucose Meter, suitable reason would be,
Patient can't see the display clearly
Patient has hand mobility issues, mean handling of machine or actually test strips are unfairly difficult.
Or for patients such as myself
My insulin pump remote is also my blood glucose meter, but all my bolus/corrections wizards software is loaded onto the remote and not the pump itself. So to use a different blood glucose meter means I would lose a lot of my pumps functions, as there isn't a way of manually entering a BG reading into the bolus/correction wizards!
So if you've got a reasonable reason for swapping back to your old meter then your surgery is obliged to prescribe test strips for it...
If you haven't then it's a case of using what's being prescribed or buying your own