去年 is very common. Though 上年 is a word, I don't recall the last time I actually heard someone use it in everyday speech. 上 as a relative time word much more commonly applies to months (上个月) and weeks (上个星期) and, of course, occurs in the word 上午 'A.M.'.
If I heard 上个年, I would interpret it as "the year before" (whatever point in time was just being discussed), not "last year" (which is always the year before the present).
离开 is always used when leaving a place, not leaving towards it. If you wanted to say something along the lines of "left home TO London" you could use 到 or 去, as in "离开家(到/去)伦敦"