Here's the thing,
P&O simply have had to go to Maleth (who >?
you may ask lol) as there are NO spare long haul charter aircraft
anymore in the UK.
Why,
TUI have vastly increased their own Fly-Cruises with their Marella brand,
thus leaving P&O up the creek this season.
P&O were hoping to use Virgin for extra Charters but this did not get going as we know.
TUI have also got 787 airframes in MX this winter to have major checks and cabin refurbs.
As for the Maleth bad reports of the 'soft product'
yes true,
P&O could have simply arranged for an
enhanced catering on the meals, and perhaps offered free drinks (but they maybe free already anyway?)
Also ensure a pillow and a decent blanket
on each seat.
We used to have for our cruise flights for P&O, or Cunard
logo headrest covers on the seats - All small things
, but the Pax do notice.
Having no IFE is pretty Naff these days on a Long haul flight, but many folk will bring a book, and a Pad to watch content,
but there is NO at-seat power 
Historically in the past for these Fly-Cruise flights we had wide bodies from Monarch, Thomson/First Choice, Thomas Cook/Condor, BA (using charter 767-300's) and even Virgin Atlantic flying the many cruise ship charters to take pax out to their The Caribbean Fly-Cruises in the winter peak season to BGI, ANU, and SJU.
Great work then for the charter airlines in an otherwise quieter period.
Now there is simply no one that P&O can turn to as TUI do not have enough uplift for even their own, nor these flights.
P&O could buy in seats (bulk amounts) on BA and VS S
cheduled flights but this costing even using the cheapest IT fares would likely be prohibitive for P&O to sustain in the long term.
Aer Lingus (MAN), and Norse (LGW), also fly to BGI but these schedules may not fit in with ''cruise ship day''.
So there we have it...
Edit - also Maleth fly their A330's in a very nasty 3-3-3 config at 345 Y (remember Monarch's A300's with 361 seats yuk)