The deal is structured as a scheme of arrangement, under which C&WW effectively cancels its own share capital and reissues new shares to Vodafone. It requires shareholder approval and the sanction of the High Court in order to do this.
"Shareholder approval" means that 75 per cent of the votes cast at an shareholder meeting - not 75 per cent of the total - must be in favour of the deal. That could easily mean the takeover gets through even if only a minority of shareholders actually vote for it. But since Vodafone is paying almost twice CWW's share price before news of the approach emerged, there's unlikely to be much opposition. The court approval is usually a formality.
If you hold your shares in a personal Crest account or in certificate form, you'll shortly receive a formal bid document, which will contain a voting form for the shareholder meeting.
If you hold your shares in a nominee account, the usual practice is that your broker will send you a corporate action message, setting out your choices and any deadlines. This may come through as an email or as a 'secure message' in your account.
If you take no action, your shares will be acquired anyway provided that the shareholder meeting and the court meeting sanction the takeover. If you hold shares in a nominee account, you'll probably receive a cash credit to your dealing account. With certificates and Crest accounts, you may receive a cheque or a credit to your bank account, depending on how you've instructed your broker. The takeover is not expected to complete until the summer.
Because this is a cash takeover, if your holding is worth more than £3,000 at the takeover price (ie, you own more than 7,895 C&WW shares), you'll be liable for capital gains tax on any profit you have made (although the first £10,600 of capital gains you make in any tax year are free of tax). There's a useful guide to shares and capital gains tax (PDF) on HM Revenue & Customs' website.