Thanks to all, It really works for me,makes sense and much more user friendly. Unless you really want it, its a bit of work.
Head Unit Wires were easy enough to reroute, as they run underneath the dash anyways. The A/C being lower wasn't an issue as the vents swivel upwards, used a plastic container and some hose to "tap in" to the ducts (from both sides) that run to the rear seats and blocked off the port that went to the original vents. This actually worked for the better as it changed the airflow directing more air to the door and rear vents (where the "new" vents). Better airflow all round now!
The Vents once detached were cut and pretty much fit perfectly into the headunit surround, with about a 10mm gap on either side, a bit of araldite to hold it all in and bog to fill in the aesthetics went down a treat. The instrument panel surround was less cooperative, had to enlarge the hole width-ways (into the speed alert cavity) and fill it in height-ways. Pretty much a perfect fit behind for a standard unit, rests right on the port (now blocked) for the old vents and just clips in. Bit of Satin Black Paint to finish it all off and it came up nice.
Real happy with it!