Everyone in the UK is meant to have the choice of 6 devices currently recommended by NICE.
This is not the case - usually because clinics will have some sort of 'deal' with a supplier or for practical reasons, such as healthcare professionals aren't familiar with all the devices and it can be difficult in group training scenarios if they are 6 people on 6 different pumps.
If there is a specific reason you want one kind of pump and that is different from those offered at your clinic you will probably have to argue your case. It also may affect which pot of NHS money your funding comes from and so may mean it takes you longer to get access to it.
This is not meant to be the case - there shouldn't be a postcode lottery - but at the moment there is.
Please see the input advocacy website for help:
http://www.input.me.uk/
All the best!