Bansko is a town, so it's correct to say IN Bansko. As for the red runs, there is a piste map on this website...
You can also check here:
http://www.banskoski.com/karta.xhtml.en
Yes is the answer to your original question Colin ~ There's the Tomba - a good black that's a challenge when the weather plays up! - and there's a whole bunch of reds from the top to the middle.
Bansko has to be the main resort in BG if you're looking to test yourself ....(unless you want to try skiing in Sunnybeach - now there's a challenge and and a half!)