Nokia 6230 won't receive MMS from other networks

I bought an old Vodafone locked & badged Nokia 6230, I think it was on some business contract before.

I had it unlocked using a cable & PC and have put my Virgin sim in it.

I've managed to set it up for GPRS and MMS by having the settings sent to me by SMS (from Virgin) and deleting the old Vodafone settings in the Active Web Settings.

MMS's still wouldn't send/receive till I found an extra setting under Messages > Message Settings > Multimedia Msgs > Connection Settings > Active Multimedia Settings, which was still set to Vodafone. I switched it to Virgin MMS.

Now I can send & receive MMS to mates on Virgin, but not receive MMS from other networks. My mate on T-mobile tried and her MMS just timed out (yet she received an MMS I sent her). I'm also trying to receive a test MMS from Virgin Train's Mobile Ticket site, which never arrives.

Please help, it's driving me mad! Virgin weren't much help when I called. Might there be any other old Vodafone settings lurking anywhere? I've looked all over.