After five minutes on the o2 Support website, helping a client. I found the following information un contact numbers, hope it is of help to someone and will save time! The problem with large corporates is that they build their websites on large enterprise systems that are not condusive to getting listed on search engines (correct as of 16-2-12).

Call us – Pay & Go

Pay & Go Customer Service Dial Charges
From your O2 mobile 4445 25p per call
From a landline 0844 809 0222 5p / min
Opening hours Monday – Friday 08:00 – 21:00
Saturday 08:00 – 20:00
Sunday 08:00 – 18:00
Top-Up Line Dial Charges
From your O2 mobile 4444 Free
From a landline 0845 606 2277 Local rate
Opening hours Monday – Sunday 24 hours

Call us – Pay Monthly

Pay Monthly Customer Service Dial Charges
From your O2 mobile 202 Free
From a landline 0844 809 0202 5p / min
Opening hours Monday – Friday 08:00 – 21:00
Saturday 08:00 – 20:00
Sunday 08:00 – 18:00

Call us – Business

Business Customer Service Dial Charges
From your O2 mobile 8002 Free
From a landline 0800 977 7337 Free
From another country +44 844 8090 200 Free
Opening hours Monday – Friday 08:00 – 21:00
Saturday 08:00 – 20:00
Sunday 08:00 – 18:00
Online Business Customer Service Dial Charges
From your O2 mobile 8002 Free
From a landline 0800 977 7027 Free
From another country +44 844 8090 200 Free
Opening hours Monday – Friday 08:00 – 21:00
Saturday 08:00 – 20:00
Sunday 08:00 – 18:00