Hi thanks for the replies.
I've checked and definately got the FR version of the Zee rd-m640-ss so should be ok.
I refitted my old shimano deore rear mech and realised that it slides onto either side of the rear mech hanger whereas the new zee mech just fits on the outside of the hanger which results in the old rear mech being around 5mm closer to the cassette with enough range to change all gears.
Do i need a different rear mech hanger for the new shimano zee mech to work with my bike frame which is a Marin Rocky Ridge 7 Four? Such a hanger may shift the new mech across by 5mm which would give me the range I need.
I'll take some photos as soon as I get to 10 posts.
Any thoughts are very much appreciated folks?
Really want to get out on the bike to shift some festive pounds!