As you probably know, they are a bit long in the tooth now:-
From C-Map web-site:-
C-Map's original CF85 cartridge is no longer regularly updated. Most cartridges were last updated in 2000 or 2001 and both the new and update pricing has been reduced to reflect this.
Please Note:
The last two digits of the cartridge code denote the version or update number, if your cartridge has a lower number than that in the list, a more up-to-date version is available.
<A target="_blank" HREF=http://www.c-map.co.uk/pdfs/master_d.pdf>http://www.c-map.co.uk/pdfs/master_d.pdf</A>
Best bet is to find some-one who has upgraded to a newer chart-plotter and has some of the old CF85's around or get C-Map to exchange your Bristol Channel ( if they still do that ).