Hi Paul, 
Great news on your continence. 
Sometimes things go quiet for a long time, but it might be worth calling your surgeon's secretary to check that you're still on the radar. 
Regarding sildenafil (or tadalafil) I think it's worth approaching your GP first, but if that fails try your surgeon again.
In my case I was batted between GP and surgeon. Eventually my surgeon sent a letter to my GP asking for a repeat prescription for Tadalafil. Over the five years since surgery, I've probably called my surgeon's secretary a couple of times or so to chase up on PSA test requests due to cancelled appointments etc..
One other thing you could try, is contacting PALS (patient liaison service) with a note of caution that in my case, they made appointments for me which were subsequently cancelled. 
Good luck, 
Kev.