Camlobe
CAA mandated compliance with SID's for all 300 & 400 aircraft from 28th September this year. You can apply for an extension upto September 2009 for non-AOC aircraft from the CAA (to try and be in line with other EASA States), and they may grant it subject to a visual, non-dismantling inspection, on low-hour aircraft, where the maintenance company has a good knowledge of the aircraft. I'm aware of two 310R's that have been given extensions - one for about 3 months, and one for 6 months. Different regional offices seem to view granting the extension differently. You may need to get your regional office surveyor to talk to CAA head of structures (Rory Martin) at Gatwick and he can advise on the requirements to get the extension.
For AOC aircraft - tough - no extensions.
Regards