Thanks for the comments chaps.
Yes, I've done the E&W (same year as you did it, MV) and agree it's a fine ride. I was thinking of the outward route of that as the return, preferring to be a bit further south and exploring the Tregaron area, which hitherto I haven't ridden.
And yes, I'm well aware of the etiquette regarding perms, Steve. If there is a suitable route set up already I will use it, and deal through the appropriate organiser. That's why I asked the question really. I know I can look through the lists of permanents on the AUK site, but as has been commented here before it's sometimes difficult to identify quite where these rides go.
And of course the etiquette of doing such a ride at all in the circumstances I described needs to be explored, as my first responsibility that weekend is to Mr Dulates's event, and I have no intention of upsetting any apple carts there. But the "option 1" above looks as if it might well fit the bill if circumstances permit.