Hi Jake,
The current moulds in existence I know of are:
E6 - Belongs to Cookie, booked up for many months - 2 boats. Also probably not available to use.
E5 - Belongs to Lucy and me, booked up for many months. It is on the Isle of Wight and is in use for the moment. 1 or 2 boats.
Slug - Belongs to the class. In Paris but available for collection any time (pending the approval of the committee). Not in amazing shape but probably good for another boat after a little bit of work. This is probably your best bet if you want a mould in a hurry. You must join the association first though. It is quite an old design now.
For something more up to date, but needing more work, the Banshee frames offered above might be best. There is not much to choose between the modern narrow hulls.