chcoffshore - both bidders have their transition plans but nothing offical will be released until the decision is made.
However, it makes sense to convert the Mk 3 flights first becaause the aircraft are older and more knackered - the 3As have better avionics/autopilot and are more serviceable.
If it were me I would tackle Valley first because the engineering there is still struggling and it would be easy to improve on the availability and look good - it also allows the bidders OCU to be establlished in its permanent location and co-locates the new management with the old (mil) meaning that in theory any difficulties with the transition process would be easier to sort in person. From there one could just work clockwise round the country.