Anyways, by distilling the info from several sites, I sussed it out. Here it is:
- Open phone app
- Preferences & Accounts
- Scroll down to Network
- Switch Manual Settings on
- Tap Edit Network Settings
- Tap MMS APN
- Set MMS APN to goto.virginmobile.uk
- Set USERNAME to completely blank
- Set PASSWORD to completely blank
- Under MMS PROPERTIES
- Set MMSC to http://mms.virginmobile.co.uk:8002
- Set MMS PROXY to 193.30.166.2:8080
- Leave MAX SIZE at 300
- Tap Change Settings
And that should be it!