Most people I've spoken to have said that they think aptitude tests bear little relevance to piloting. I have done the full set at Cranwell recently (you do some of them for the GAPAN thingy) and I thought they were fairly easy, but as I only have 1hr TT, I dunno about whether they are worth doing. The RAF make a good case for them.
I have a friend who's just about to start flying training on a good sponsorship and she said she only got average scores on the aptitude tests. So even if you're not great at the tests, you could well make an excellent pilot anyway
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Good luck.