3engnever, the aircraft which will be 'moist-leased' to Thomas Cook will be a Voyager KC2 in air transport configuration, but with a 323-seat 'sell 'em cheap, stack 'em tight' grockle-fit cabin configuration. It will not be a plain-vanilla A330.
It will painted in white, with Thomas Cook logos.
Depending on ZFW, the A330MRTT is supposedly able to carry 111 tonnes of fuel, whereas the TriStar (IIRC) could carry up to 136 tonnes - but had a higher burn rate.