Retired also , but memory says ..
Full polar survival pack [ 3 rows of 4 seats ] if more than 700nm from an Adequate airfield
[ does not have to be Suitable ,...... -40C , 200m blo snow ! ].
Japan - UK , North of Novaya Zemlya , 550nm from NPOLE , 698 from Adequate ... no polar pack .
Re fuel temps . Siberian High would sometimes mean you needed to go up to find warmer air .
Fuel ex USA , sometimes had freeze point -41C . Europe elsewhere freeze point -47C .
Memory suggests don't let the fuel get closer than 3 or 4 degrees from freeze point .
Fly faster was always welcome . To warm the fuel , of course .