From my Belfast Pilot's Notes:
Water-Methanol injection system
Tanks (four) ........Fibre-glass
Capacity..............62.5 gal. each (250 gal. total) Spec.D.Eng.RD 2491)
Reading the blurb reminds me that (in basic terms) the system allowed sea-level power to be maintained up to 10,000 ft amsl for 4 minutes.