If it’s on the MINI Website, then you can order it, there are a wide choice of seats and wheels but it comes down to what “spec” you choose, Classic, Sport or Exclusive as all have different options.
As far as I remember when we got ours, all colours are included as are the choice of roof and mirror colours, but you pay extra for bonnet stripes and Bigger Wheels
Play with the car designer and you can see what each looks like
https://www.mini.co.uk/en_GB/home/range/select-your-mini/mini-5-door-hatch.html#iframe