How Can I Consolidate My iTunes Account?

When I first tried to link my Apple TV to iTunes Match (when it first appeared in the UK), I could not do it with my iTunes account, even though I had signed up to it. Upon scouring the Apple forum, I learned that a few people were having the same problem and that by signing in with the first part of their iTunes account name (ie. 'johndoe' instead of 'johndoe@mac.com') they found that Match would connect. This worked for me. Since then, however, my account has become bifurcated, with some apps only updating on the shortened account name and some on the longer. My iCloud seems to like both names, except for Photostream on the Apple TV which insists on the longer name. iTunes Match now only signs in on the shorter account name. For a few weeks GTA III refused to work or update on either. They both share the same credit card details.

I have tried to amalgamate the accounts by deleting the longer account name on the iTunes Account page (and expected to lose some content), but even though I was allowed to do it, the two accounts still exist, presumably because it is actually one account as far as the system is concerned.

At the moment, this is merely an inconvenience, as I have to sign out and back in to update certain apps, then do it again and go through the rigamarole of adding my computer back to iTunes Match. In the future, though, it may cause more problems. Any ideas? I tried phoning Apple a couple of times, but I simply cannot get the people on the other end of the line to understand what my problem is.