The "A Space In Time" album (with "I'd Love To Change The World") came out in 1971, I think. I was a huge TYA fan in high school, and have all of their original albums on vinyl. Alvin Lee is a great guitarist, although some have argued that his playing is a little repetitive at times. But he sure is fast! I saw TYA live in Chicago, sometime in the early 70's. It was after the album that had Choo-Choo Mama, and Back to Birmingham on it - I forget the name of that album. But basically towards the end of their peak years.
Interestingly, the other three members of TYA have been touring again in recent years, minus Alvin, using the name TYA. (Leo Lyons on bass, Chick Churchill on keyboards, and Ric Lee on drums.) Even though the other three are pretty good musiciians, Alvin was obviously the heart and soul of the group, as guitarist, vocalist, and songwriter. So this "new TYA" didn't sound too promising to me. But I went to see them a year or two ago at the Sausolito Art Festival. They had found a younger guy named Joe Gooch, who replicates Alvin's guitar style very well, and even sings reasonably like him. So it turned out to be a great show, with all of the big songs being covered.
My overall favorite TYA album remains "Cricklewood Green", with "Ssssh" and "A Space In Time" being right up there. Their double live album is also a pretty good capturing of a TYA concert. One obscure album is their "Undead" (get it?) live album, which was actually only their second album, and was recorded in a little club in the UK. Most of it is more jazz-oriented, although it also has the "original" (pre-Woodstock, I think) version of "I'm Going Home". Played a little less frenetically than later versions, but in my opinion it's a better version by virture of being a tad slower-tempo'd. Also check out the version of Woody Herman's "Woodchopper's Ball", which Alvin and company just rip through.