You can try getting the pump from your GP - some might be prepared to order it without the ED clinic paperwork.
The prescription part numbers you want are most likely 15019 (pump itself and accessories), and 15222 (3 spare Surefit constriction rings - it only comes with 1 and these are consumables and ideally go on repeat prescription).
You might also try contacting the ED clinic and ask to be put on the pump clinic list, which is usually much shorter as they're run by the pump company reps rather than the NHS.
If you do order the pump yourself, make sure to ask for it zero VAT rated (medical appliance) and not 20% VAT rated (sex toy).
The pump cost includes having it demoed on you by the iMEDicare reps, both prescription and self-purchase. Research has shown that this doubles the number of people who use it successfully, and some NHS areas will only allow it to be prescribed after a pump clinic session where they offer to demo it (you don't have to have it demoed on you, but in those areas, you do have to attend the session to get the paperwork to take back to your GP). If you buy it privately or on prescription and don't get the demo, you can call the company and ask for it. It they find you needed an extra large model, they'll usually swap the parts when they demo it. (If you attend the pump clinic first, they'll order the right size parts in the first place.)
In terms of PDE5 inhibitors, they aren't going to be as useful for you because of the no nerve sparing, but you could try asking for Tadalafil or Sildenafil. Generally, Tadalafil are the more useful of the two for their healing properties, and therefore better to try first if you can get them.