Was unable to do performance review this year as my manager resigned & then I went overseas on approved leave. While overseas, HR processed my performance review. When I came back, I told my next level manager & he kept assuring me I had nothing to worry about. But when it came to pay review, I was not given a pay rise. Now HR & management says it was because I was rated below target in performance review. When I disputed, they found small faults which were never mentioned to me. Is this unfair?

Hi there. Without being a HR specialist, it sounds very unfair. One thing you need to keep in mind is that your review period should only be reviewed on the pro rata basis that was available (ie ex holidays), however that said if you were never informed of any shortcomings then there should be no reason to not be rewarded ( at least) the average level.
To take the matter further, I would encourage you to assess your expectations based on previous years. If these have all been good, then throw in the discrimination card It is not your fault that your Manager resigned, and do not hesitate to ask why he/she was not requested to complete staff reviews prior to departure (whoops, do we now have Senior Management negligence)
From my view, you have no legal standing, but hoping that these comments provide some thoughts on your next personal approach.
Good luck
Ken