Help me with gap jeans size

[Nion]

I'd like to try these
www.gap.co.uk/gap/mid-rise-classic-straight-jeans-with-washwell/000352700.html?dwvar_000352700_color=000352700000&dwvar_000352700_fit=regular&cgid=
But cannot figure out sizing and the size guides are useless. No chance of getting to a shop soon.
I'm waist 27inch hips 36inch. My levi 501s are a 28 and fit nice. Recently tried a similar pair from uniqlo in a 27 but they were big and honestly pretty ugly.
Based on model sizes reported on the gap link, I think I'd need a 30. Anyone any experience?

Gap jeans sizing is bizarre, and the labels never seem to match what it says on the website. If it helps, I normally wear a 27 elsewhere (somewhere between size 8-10). In Gap skinnies I wear a 26, after much trial and error and sending things back.