We were the support band for this gig, I think we were called "Prairie" at the time. We were trying out our newly acquired Sound City 100 watt stacks and mostly original material but were amazed to see Queen were still using battered old Vox AC 30's and playing rock'nroll covers!
As Brian May has recalled there was next to no audience, and we were in the bar for most of their set as they were for ours. I recall Brian May being particularly friendly and interested and I believe he came to see us when we played "The Greyhound" in Fulham later that year.
I believe we both got GBP 20 for the gig!