The event doses of the PDE5 inhibitors, Sildenafil (Viagra) and Tadalafil (Cialis), will only work if nerves are working. (The daily 5mg dose Tadalafil is still worth using even if nerves aren't working yet, as it helps preserve the penis for when they are, similarly to the vacuum pump.)
For when you are still waiting for nerves to recover, the options are vacuum pump with cock rings, or a vasodilator drug such as alprostadil, which is available in many formats - penis injection (e.g. caverject), urethral pellet (Muse), and a cream for urethral insertion or topical on the glans (Vitaros - not sure how available this is in the UK).
Vasodilators are only available under supervision of ED clinic as far as I know - there's a risk of them being too effective and causing permanent damage by generating an erection that lasts too long (4 hours) if too high a dose is used, so you start low and work up to the dose which works for you. They can cause a painful penis in some people, and can cause pain in a partner too in some cases (in which case a condom can be used).