Chris, two quick comments ....
0.018 is 'undetectable' .... so fantastic news and congratulations!
If you have had all nerves removed then there is no point taking Viagra or Cialis; they won't work without nerve bundles or a small miracle. Push for a vacuum device and/or muse pellets / Caverject injections, none of which depend on those pesky nerves. (Perhaps the nurse could confirm for you whether the registrar was correct when he said all your nerves had been removed)
Would the RT trial require you to also have HT? Pretty significant differences between RT on its own and RT/HT for many months or years. If it is any reassurance to you, John waited two years between the op and the salvage RT/HT and I think that gap gave him time to recover from one treatment, get fully fit again, and then believe/accept that he did indeed need the salvage treatment. Each to their own of course, and some men do go straight for the trial but really, why put yourself through even more unpleasant side effects unless you have to?