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Without being able to view stats on the domains in question, it is impossible to give you the best advice. Generally speaking, subfolders get better results than subdomains, but there are many other factors to consider. If you can't move to a subfolder structure, then skip this issue and start down the list of other technical optimization best practices. With time and traffic, I'm sure you'll gain in your organic rankings for selected keywords. In my experience, a domain name is but a small factor of the overall picture. The issues you'll have with these subdomains are more of a marketing cost than an SEO cost.

Thanks again Alan. I've checked the site with screaming frog and it doesn't return any url's with parameters so at this stage I might be ok.  I am getting a message in webmaster tools saying "severe health issues" but it doesn't appear to be affecting the urls I want to keep.  I'll likely remove the entry once things have cleared up some more. Thanks Jeff At the moment I'm stuck with Zeus web server (insert expletives here) so no htaccess file or I'd be in a better position.  After messing around with it and very limited documentation I can only get the site operating with index.php in the url but with SEF url's for the remainder of it.  I'm investigating migration to an apache server so that might make it easier. Regards Ian

Thanks Tom That's a good point.  Part of my problem lies in the number of URL's with parameters (thousands).  Applying status codes of any type isn't really viable. Starting to see the url's clean up with the addition of the entries in robot.txt. Regards Ian

Thanks Mike. I think part of my problem is that being a CMS a lot of the code is automatically generated.   Therefore the code in the header of the blog archives is the same as the code in the header for a blog post.  Therefore I guess I'm stuck unless I can find some kind of SEO plug in for Umbraco.  It was set up by another web company so I'm not very familiar with it. If anyone has experience with this situation in Umbraco I'd love some advice. Regards Ian