Cheers for the info
No split pair situation here I'm afraid, 2nd engineer arrived shortly after your post, believes it's just a particularly "hot" trunk.
Attempted fix was to splice from a different trunk running adjacent to the EO trunk which serves my building; upshot is I'm now connected to a cab about 300m from the premises; D-side back to the exchange had an AC Balance of around 70, but still only syncing at 10mbps, with a ridiculous amount of errors.
SF: 192183 183353
SFErr(CRCErr): 124188 0
Line is also rather unstable; SNRM drops to virtually nothing intermittently, leading to a large number of tones being dropped. Throughput drops to 1-2mbps during these periods, although it does eventually recover. Forcing a resync at this time will cause the line to sync at around 5mbps, although SNRM eventually climbs back up to around 12, so it looks like whatever the issue is, it's causing around a 6dB drop in SNR when it occurs.
Upshot of it all is that the engineer seems to think there's a significant issue with the internal wiring. Building management / landlord aren't likely to make the effort (or spend the money, rather) to resolve it, which means it's probably going to be down to me to inspect, repair and/or replace the length from the DP up to my flat :-/ Unless there's anything else at the exchange that you think might be worth checking?
Also, any advice RE: test equipment to check for internal wiring faults? Obviously I can visually inspect for things like physical damage to cables, loose terminations etc, and can check for continuity, but I'm thinking more along the lines of AC balance, resistance and capacitance.