They are currently undergoing quite a substantial upgrade program to attempt to ease congestion in the worst hit areas. Or so I have heard anyway.
Plus, see my thread about o2 being slow recently ( EDIT, just noticed you have posted in that ).
There was an outage causing huge hassles in the NW a day or so ago, I believe some cables were accidentally cut through somewhere.
This caused a fair amount of slowdown and the Scottish network was apparently routed through the same location so it had an effect on us up North of the border too.
Check the o2 forums and ADSLGuide boards - same thing being reported there by many.
have U got a link to the o2 forums? can only find dontbethere forum & thats made of chocolate..