well, I have heard to 75 and 79 only, but before writing that first line, I for sure had a look at MrScully's queenconcerts.com and found out, that one concert was in 1973 at Hammersmith too. I dont know actually, if there is a recording available...
(just have look there - link, all-in-one filter - choose "London" and look at year 73 - there were 2 shows - afternoon and evening)