I read somewhere that certain of the extinguishers are unacceptable this year. I meant to mention it to Iain C but forgot. I will try to track down where I read it. I seem to remember thinking that the one in my old car might get captured.
I did a bit of research on this back in the Autumn when I was trying to figure out where best to site the extinguisher bottle, how big it needed to be, etc. The regs seem to have been fairly static other than a requirment for FIA homologated cars to have 4 litres. Figured out where to put a 4 litre just in case...
Had a quick grub on the RAC MSA website and found that there doesn't appear to be any changes this year in the regs. After a bit more digging I did come across this article: www.msauk.org/admin/news/ViewNews.asp?NewsId=1080 It appears that old Halon filled fire extinguishers are banned from January this year...AFAIK they've been banned from new installations since at least 96.
Dave - you'll surely be able to pick one up off Iain cheaply - it won't need to meet the new regs for your track car. I'll do you a deal if mine is out of spec - if not, I'll tell Iain to keep the best one spare for you.