From what I understand, if you connect using mIRC 7.1, you should be in a channel that looks exactly the same, but without the other users. In your case, the channel looks different.
You might want to check with your network operators to see if the network supports UTF8 at all. If they don't, you're out of luck.
If they do, you still won't be able to join the old channel, but you could try to get everyone to join the new channel.