Yes, sprucemoose, I think that the A330-200 will certainly make an excellent tanker. But the RAF should be buying them, not renting them.
A310MRTT will indeed be an excellent, efficient and economical 21st Century tanker-transport even in its current form. It would be still better with the FedEx cockpit, a revised FMS, a more integrated MCS, together with Link 16 or better...
Agree with you about the KC-767 though!