Some resources that may be useful
CAA Safety sense leaflet on ditching which has a lot of good advice and information in it:
http://www.caa.co.uk/docs/33/ga_srg_09webSSL21.pdf
GASCo sometimes runs ditching courses. I went on one at the RNLI College. I found it a big eye opener on this issue. As has been said in other posts in this thread the big problem isn’t getting down safely onto the water but staying alive once floating about in it.
GASCo - GASCo Goes to Sea
There’s nothing quite like struggling to get into a life raft while cold and soaking wet to realise just how tricky it can be. A raft can throw in a few tricks in its own such as turning upside down and trapping you under it.
SEMS led the pool work I took part in. They run training courses and can hire out or sell equipment:
SEMS Aerosafe - Survival Equipment for light aircraft