He has treatment scheduled for a few months time; the delay is part of the treatment protocol, so he is NOT on a waiting list, he is 'active treatment' (even if not much is happening yet!)
Nationwide do a great travel insurance policy: there will be an extra charge (rather than free), but it's pretty competitive - if you have any account with them.
If he's having HT by injection, he WILL have side effects, such as fatigue, hot flushes and night sweats (they are close to universal). But they're no reason not to carry on living, quite the reverse!