Seaphoon was an option years ago when the French wanted to have the capability in Eurofighter and we nixed it (they buggered off not long after) because we didn't need carrier borne EFA, ooops.....
the French requirement was for an aircraft which could operate off the Foch, which limited weight/size to thr size of the Rafale. The other EFA partners, not just the UK, needed an aircraft which couldn't be built within that limit, which is why the French walked. Not a UK decision and if the French had looked beyond the Foch the EFA could have been radically different.