Many RN guys do UAS, JEFTS is only ever done after IOT for either the RN, RAF or Army (a shorter course). Whether you want to study as you fly is your choice, and that of the UAS you apply to. Hope this helps.
Edited to also apply above full course JEFTS / UAS to booties (Royal Marines!)
[ 01 November 2001: Message edited by: bad livin' ]