Advice about CGT in relation to a Vodafone offer

[nong38]

Vodafone have sold their interests in Verizon Wireless to AT&T, Vodaphone will return £71b to shareholders, I will get a capital payment returned to me, I can choose to have this payment treated as normal income tax or CGT. I have never used my Capital Gains Tax allowance but it would be well under the annual limit so it seems that it would better to take this route and avoid £400 of income tax. Can anyone tell me if it is as simple as that or is there something I need to know about CGT, do I have to register for instance? I do not have an accountant so I hope someone knows there way around and cane help me decide which option I should take.

Thanks for any advice forthcoming.