Your GP can't put you on a pump, it would need to be done via your hospital diabetic clinic.
Hospital clinics usually only offer a limited selection of pumps. To train patients on how to use the pumps the diabetic specialist nurses need to have been trained on how to use the pumps. They aren't trained on all pumps, just the pump models that the clinic offers.
So if you want an omnipod, find out what hospitals in your area support the omnipod. You can probably find this out by contacting ypsomed, the omnipod distributor in the uk -
https://www.mylife-diabetescare.co.uk
And then consider whether you actually fill any of the criteria for pumping -
http://www.inputdiabetes.org.uk/alt-insulin-pumps/nhs-funding-pump/
If so, ask your GP to refer you to an endocrinologist at a hospital that supports omnipod.