well the RYA has sea time requirements and they have been noted in this thread already, proof is a from a discharge book, RYA log book, PYA log book or and other method like letter from employer etc or just type up your own log!
It doesn't need to be a RYA sea survival, a MN, seafish or a RNLI one would do, also the medical can be a ML5 , https://afrmmcanet.mcga.gov.uk/formspublic/MSF4112.pdf
, that your doctor completes and is limited to 60nm offshore or a MN ENG 1 at a specialist doctor, http://www.mcga.gov.uk/c4mca/ds-shs-mgn_264-2.pdf
, for upto 150nm offshore.
the first aid has to be at least 1 day so if you have done with RNLI you would be ok.
These requirements do not come from the RYA but the government via the MCA as extra training for a commercial endorsement.
do you need a commercial endorsement?