Currently it's not illegal if you aren't using the phone for communication, which is how Jimmy Carr got away with it, by saying he was taking notes. Anyway they are changing the law soon, so point taken. However voice control of mobile phone is fine.
I did see that video on converting to bluetooth, looks too complicated and still using the old guts of it, which are pretty pony I believe. Also I don't want to potential screw up my OEM headunit, they are worth silly money on Ebay I noticed.
One problem I can see with some of the options present so far, volume or track control needs to be from phone, which means not while underway as that is illegal.
Id like a controller of some sort on or under dash within easy reach.
As for keeping oem headunit, there was a video from Classic Mini Workshop showing how to add bluetooth onto the phillips mini (or rover equivalent) headunit. Needs to be dismantled and the BT board soldered into headunit board, but it was a completely stealth setup.