At least use the address .
I did that and that's how I managed to find out the cabinet is full.
Postcode checkers simply say "fibre is not available in your area" (when I know it is, as I've had it for 2.5 years).
So, yes, you're right - the address checker is more reliable and is the only one to give the 'true' answer (that the cabinet is full and capacity is being added by 26th Feb).
I get the following result...
FTTC Range A (Clean) 80 69.8 20 20 -- 26-Feb-14
FTTC Range B (Impacted) 79.9 53.8 20 19 -- 26-Feb-14
So, even though the cabinet is full (so; a fair bit of cross-talk, I'd imagine - especially as most lines will come this way) I'm still syncing within the 'Clean' range (with average throughput between 62-66Mbps).
Last time I checked my sync (and the throughput hasn't dropped since) it was around 76Mbps.
At least I know what to expect when I add a second line (will probably go for a 40/10 line on that one, to reduce the cross-talk effect on MY home 80/20 line - no need to go higher than 40/10 as everybody else, in the company, has ADSL2+ connections and the fastest of those is less than around 4Mbps).
Roll on Feb 26th - will probably go for a Zen 40/10 connection (if they do new line installs) as I need a static IP (a dynamic DNS won't do in my case, as we'll all need remote access into several sites and this will be filtered by IP).
vDSL2 FTTC Infinity with BT
DL Sync 78Mbps
UL Sync 20Mbps