ancientaviator62,
After some headscratching, and combining reference to my authority - "Vengeance" (Peter C.Smith) - with what I remember, the facts are as follows (Mks. I-III [A31], and I don't think Mk.IV [A35] varied).
Normal tankage 220 US gallons (183 Imp) - PCS says 200 (Imp) - best we ever did was 60 galls/hr (Imp) in cruise at 160 mph ~ 490 miles.
PCS makes oblique reference to "400 galls full tanks". What can he possibly mean ? Never saw or heard of any external tank: why would we want one ? (apart from an old story about a DIY attempt sometime in the past - the things created so much drag that you got no further with them on than you did before). And there was no "spare" internal tankage !
1200 miles ? In your dreams ! Danny.