Today I ordered all the electronics on HobbyKing (yes, even from EU this is the best shop to buy RC stuff from).
Unfortunately the implellers were not available, so I ordered something a bit smaller (which is also good because it doesn't have the problem of fitting in a smaller tube: Replacement fan for 2.5inch/64mm EDF (7blade). I also bought the shafts as I don't think the ones in the motors are long enough for the fan.
For the ESCs I found that Turnigy made a newer, better, more programmable and cheaper ESC, so I bought it instead of the one in the BOM: Turnigy TrackStar 18A 1/18th Scale Brushless Car ESC.
It has the same current specs 18A, reverse, 2-3 cells LiPo, but is a 3 dollars cheaper each (almost 10 dollars for 3) and more programmable. It has less burst current (25A vs 50A) but I doubt our motors in the ROV will ever need such a burst current.
Once I receive it I'll see how it works and will let you know.