I reckon compact as we know it is definitely post '87, so to satisfy the scrutineers, that's out. Was a nuovo record triple available? I know a C record triple was available at around that date??.
You can go down to a 41 on a NR chainset and a 28 at the back, which is considerably lower than what you have. Your other option (breaking the NR groupset of course) is to fit the tourists favourites of TA or stronglight or maybe a 1st gen MTB chainset.
Personally, I'd keep the bike campag NR and fit the 41x28. You can do it, in the same way we rode the peak district on 42x21 - now 39x25 can seem overgeared; you'll achieve it on whatever you have.
Actually, a compact will be fine as the scrutineers are looking for downtube shifters, quill pedals and exposed brake cables so in theory you could ride a brand new Mercian as long as it had the above.
I'm still a little conflicted as although I agree that better to keep it 'pure' but the knee saving potential of a compact is pretty enticing especially as the 48t 'big' ring can be used a lot to look like a strongman.
First step is fitting the 28t though I reckon.