I believe the only two seaters used on the Battle of Britain film were G-AVAV and G-AWGB. I think G-AVAV suffered an in flight fire whilst being flown by Connie Edwards before the move to France to finish filming so it looks like G-AWGB is the most likely candidate.
EN398 is actually MA793 which was/is owned by David Price. US registrations are NX930LB previously N930LB previously in South Africa as PT672 ex SAAF 5601 and prior to that it had originally been delivered to 6MU on 21-7-43 and then passed to the USAAF in Casablanca.
MK297 was damaged by fire in the fire at CWH in 1993. It was previously with the Confederate Air Force from 1986 as N9BL previously N9BL and N1882*. Prior to that it was our old friend from the flight magazine ad in another posting G-ASSD which was ex OO-ARD, Belgian AF SM43, Netherlands AF H-55 and H-116.
* I am a bit suspicious of the US registration N1882. I believe that all the Spitfires used in the Battle of Britain film were given fictitious N serials so I think it likely this is the serial number carried for the film although it is possible that this was subsequently used as its US civil identity.
The info for MK297 and EN398 came from http://www.supermarine-spitfire.co.uk.
The other bits are from memory.
I think it will prove difficult to identify the other B of B film Spitfire unless someone reads this who worked on the film and has a very good memory.