Internet rices are changing on P&O see below new prices on Arcadia and I believe also now on Ventura. At those costs I would suggest as others have follow the crew to the free wifi spots either at port or in town or find a cafe/bar with free wifi, it will definitely be cheaper to buy a drink and enjoy the local ambience.
For anyone going on a P&O cruise (UK), I just wanted to share some Wi-Fi information. P&O have done away with the previous packages and now have three packages on offer, all continuous 24 hrs.
The basic package is for Social media and messaging. This costs £7.75