Need Help With WP Domain Mapping (Prepared to Pay!)

Basically I've messed something up big time. I (did have) a multisite install that I'd managed to do myself and was initially trying to map a subdomain so I could begin with a big html 2 wordpress migration project but I clearly didn't know what I was doing and ended up deleting a site I hadn't yet backed up (thankfully it's fairly new and I've got the txt files so I can have it back up in a few days).

However, when trying to sort out the domain mapping blunder so I could then begin rebuilding the new site I've messed something up further and now get the error "The domain mapping plugin only works if the site is installed in /." and can't access my dashboard. I can remedy this by deleting the domain mapping plugin via FTP but then of course there is no option to sort the mapping blunder out as it's not part of the settings/tools .

I'm stuck :confused: but I'm hoping a WP guru may be able to sort it fairly easily so I'd love to hear from anyone who thinks they can help! (everything else in order for the network features and domain mapping to work are already in place like the edits to the wp-config)

EDIT - After a little reading up it appears I've actually mapped my main domain in which wp was installed which is why I'm getting the error, one article has mentioned the need to remove the entry via phpmyadmin however I think this is beyond my capabilities!