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It's a good price for that fork. As for the travel, Cotic say that 100mm is minimum, 120mm is optimal, and 140mm is the max. Ideally, you might want 120mm, but I'd rather have a shorter travel fork that worked well, than a longer travel one that didn't.
If you can find something decent in a 120mm length at a good price, then get that. From a ( very ) quick search, I didn't notice anything like that for less than around £350.
15mm through-axles are better, as they hold the wheel more securely. So something more like this one:
https://www.merlincycles.com/rockshox-reba-rlt-fork-sale-275-100840.html