Thank you to everyone who gave me tips. The nasty Seymore is, for the moment, dead!!
I gained Hastega by going up and down the mountian a few times.
During the battle I used hastega, shell, protect and Wakka's silence buster. It was brillant. I didn't even use all my aeons or my character's overdrives. You could have knocked me over with a feather when the overkill sign came up!!! Took me half an hour in total!!
Thank you to all yet again andno doubt I shall have to call on your expertise again at a later date.
Kerrie