I've just looked up my website in Google, to see if the sitemap had changed to reflect some new content and pages, and I have a bit of a problem. I use a third-party hosted toolset, which is linked via a CNAME record on my host server.

So lets say...

My Site = www.mysite.co.uk
Toolkit = www.clients.mysite.co.uk
The CNAME on my host says: clients.mysite.co.uk > thirdparty.toolset.com 

But when I look at the Google sitemap, I see several of the clients.mysite.co.uk pages listed as well - many of which I don't actually use, and so don't want the public to see.

I can't make any changes to the third party site, so can't put a robots.txt file in the root of clients.mysite.co.uk (as it's actually thirdparty.toolset.com), or make any changes to the .htaccess there either. Of course I can make changes to anything in the normal www.mysite.co.uk domain...

Any idea what I should do to stop the indexing happening in the subdomain, and also preferably to quickly remove what has already appeared in Google?