I'm bricking it, but on only slightly.
I'm bricking it quite a lot.
We got up Yorks Hill on the tandem yesterday but I'm not sure that translates to managing this.
Whilst there are a number of very, very steep hills, as is the way with these things, they are all mercifully short and using the 24, or even 48 inch gear in your case, will only add a few extra minutes onto your ride. The staircase and the one after it are steep obviously, there's one tricky right hand turn onto a road towards Cwmystwyth where you're climbing already and you have to make a right onto quite a steep ramp from memory.
There are plenty of much longer, more gentle ascents as well.
But, there are so many amazing views that you'll forget everything and just enjoy it - Irfon Valley in particular is mind-blowingly beautiful. You're going to be just fine - you know what you're doing!