Hi
Really must visit more often.
Not too sure when, probably about 1971/2, my cousin Mike was into them and I remember hearing LZ2, which I loved eventually bought it myself, then LZ1, LZ3 was to me a disappointment at the time.
Mike took me to see them at Ally Pally just before Christmas 1972 can't recall which date exactly but probably 22 Dec as I seem to recall they played Thank You which I don't think they played the next day (he had broken up with his Girlfriend so had a spare ticket), pretty much hooked after that saw the again twice in 1975 Earls Court and first Knebworth.
Been listening to them on and off ever since, advent of the internet and free downloads has been a real bonus for the live stuff which was always difficult to come by.
Andy