It's legit. I got a Gan 11M duo for £30 (bargain) plus a free Christmas Tree puzzle. 100% worth it. Shipping took a while as it was from China, and the order took a while to process, which really sketched me out, but after a quick email to support, it was sorted. (I think it's just one guy in China running this site as a side business)
This site is a scam that doesn't send the product people had ordered! Go to speedcubeshop.COM, not. co.uk,. COM they will actually send you guys the products.
Here is a link explaining it a bit further: https://www.youtube.com/watch?v=kSN9iVg8aos
Answer: Email support@speedcubestore.co.uk For me, they responded within 24 hours.