I think the last non-nomex flying suit was the Mk 7 lightweight suit for tropical climes. I had 2 in FEAF - they were great as no matter how much you perspired, as soon as you landed it was straight under the shower and then leave it on the hangar in the locker room and it was dry in next to no time. Despite the best efforts of supply (?) wing I still had them for a tour in Cyprus inthe 70's, but even though almost everyone else on the Sqn wanted one they were no longer 'in stock'. Eventually had to change them and only nomex suits (ISTR Mk 11) were available.
For interest there was a film at the Survival School at Mountbatten (then St Mawgan) showing the fire retardent properties of the nomex suit and what happened in fires etc - after seeing that I never wore anything else for flying, with the appropriate kit underneath as well!