Looked to be about 1" diameter, maybe 2" (which, compared to the tiny cables which feed individual homes, is 'massive').
Still can't imagine how they've already ran out of capacity on a relatively new cabinet when there hasn't been (and there are no plans for) any building/housing developments for years.
Equally; I can't imagine why they're bothing to install a fibre to a cabinet which has its FTTC enablement dates subject to continual movement (so far it's gone from Dec '10 to Jan '11, to March '11, to June '11, to July '11, to Sept '11 - All bets are off as to when OR finally get round to doing it)!
ADSL2+ with BE
DL Sync around 4.8Mbps
UL Sync 1088kbps
DG834GT with DGTeam firmware