Mine get added automatically but I have used the following in the past:

Press 'Menu'.
Tap 'Settings'.
Tap 'Wireless Controls'.
Tap 'Mobile networks'.
Tap 'Access Point Names'.
Press 'Menu'.
Tap 'Add APN'

Now key in the following settings:

Name: mobile web
APN: mobile.o2.co.uk
Proxy: *LEAVE BLANK*
Port: *LEAVE BLANK*
Username: web
Password: password
Server: *LEAVE BLANK*
MMSC: *LEAVE BLANK*
MMS Proxy: *LEAVE BLANK*
MMS Port: *LEAVE BLANK*
MCC: 234
MNC: 10
APN Type: default

Press 'Menu'
Tap 'Save'

Press 'Back'.
Press 'Menu'.
Tap 'Add APN'

Name: O2 MMS
APN: wap.o2.co.uk
Proxy: http://wap.o2.co.uk
Port:9201
Username: o2wap
Password: password
Server: http://mmsc.mms.o2.co.uk:8002
MMSC: http://mmsc.mms.o2.co.uk:8002
MMSproxy: 193.113.200.195
MMS port: 8080
MCC: 234
MNC: 10
APN type: mms

Press 'Menu'
Tap 'Save'

Keep tapping 'Back' until you're back at your Home screen.
Restart your phone and you should now have G/E/3G/H internet access as well as the ability to send/receive MMS. There is a problem with MMS on Android that limits image resolution to 160x120. Last edited by Zenith on Thu Sep 10, 2009 8:26 pm, edited 1 time in total. ​

 

As the phone is supported by o2, the settings should be applied automatically. The only time I have ever had to enter them is when I have used a phone not stocked by o2.

May be worth giving o2 a ring and they will send the settings, or try a hard reset if you don't mind having to set the phone up again (assuming you don't have a backup).

I will check every entry i mine and repost later.

 

Just compared the old setting I gave you with the ones in my Desire S and there are some differences. May be worth trying to enter again from the following taken from my pohione settings - sorry the first set (that have worked in the past) didn't work for you, but hopefully these will. I have marked in red the different settings from the first list.

Press 'Menu'.

Tap 'Settings'.
Tap 'Wireless Controls'.
Tap 'Mobile networks'.
Tap 'Access Point Names'.
Press 'Menu'.
Tap 'Add APN' ​

Now key in the following settings: ​

Name: o2 mobile web
APN: mobile.o2.co.uk
Proxy: *LEAVE BLANK*
Port: *LEAVE BLANK*
Username: o2web
Password: password
Server: *LEAVE BLANK*
MMSC: *LEAVE BLANK*
MMS Proxy: *LEAVE BLANK*
MMS Port: *LEAVE BLANK*​

MMS protocol: WAP 2.0

MCC: 234
MNC: 10 ​

Authentication type: leave blank

APN Type: default,hipri​

Press 'Menu'
Tap 'Save' ​

Press 'Back'.
Press 'Menu'.
Tap 'Add APN' ​

Name: O2 MMS
APN: wap.o2.co.uk
Proxy: LEAVE BLANK
Port: LEAVE BLANK
User Name: o2wap
Password: password
Server: LEAVE BLANK
MMSC: http://mmsc.mms.o2.co.uk:8002
MMSproxy: ​

​

82.132.254.1

MMS port: 8080​

MMS Protocol: Wap 2.0

MCC: 234
MNC: 10
APN type: mms ​

Press 'Menu' ​

Tap 'Save'


​

 

After 2 years on the same sim only contract, I 'upgraded' yesterday to a new, cheaper sim only contract but offering me more of everything on o2. Seemed a good deal.
However I lost all mobile data and MMS the moment the upgrade went through. I had a text then to say if I wanted to access them from my phone, to call customer service for the settings, or look on the website for manual settings.

My phone is a HTC Desire HD. The website does not have this phone, only the Desire, or the Desire S. Over the phone, they would not help as they do not stock the HD, and suggested a google the settings, contact HTC to see if they have some, or BUY A NEW PHONE!?! Apparently there is nothing they can do?! Googling brought me here, but I have exactly the same settings as posted above for their Desire S, however it does not work at all still. It was working fine until last night, so I cant understand what the problem is!

Looks like i'll be calling into an o2 shop next week or will have to try and cancel the new contract as the whole point of the upgrade to a sim only tarriff with extra data allowance on was to use on my current phone!
Until then, does anyone have any other settings to try for a Desire HD on o2 pay monthly?