No refurbished Mini's at all in the US store right now. But B&H Photo (large US supplier) has new 2018 base i3/128gb Mini's for $629, which would be 503 pounds at current exchange. Of course, US prices don't include tax, which in my state would raise the real price to $673 or 538 pounds.
I got my 2014 2.8ghz/8gb Mini for $500 (new) during a big sale at B&H last year. At that same time, Apple was selling the exact same configuration as a refurb for over $800! Now, that was unusual, due to the sale. However, several years before, I got another new 2014 Mini from B&H and the price was only about $25 more than a refurb from Apple, so I got the new one instead. Apple refurbs often aren't all that compelling in terms of price.
Also wish the mini had a discreet GPU, and this will likely push me to the iMac when I finally upgrade, especially since all my screens are very old. I really don't understand why the Mini can't be like an iMac without a screen.