Hi cgk1, used to be the following but i never use mms so not sure if it's still valid.
Access Point Name: mms.three.co.uk
Username: blank
Password: blank
Gateway IP (proxy) address: 217.171.129.2
Port number: 8799
MMS Message (Relay) Server URL:
http://mms.um.three.co.uk:10021/mmsc
Hopefully it may be of some use to you.
Alternatively give 3 support a tweet on twitter
@ThreeUKSupport
They are usually very helpful.
I know the Nokia network app was pulled but if you do a marketplace search for network, is it still missing ?