There hasn't been a kit-type solution for A/C on a MPi Mini since around 2005. Heritage Garage had probably the last Astro Air MPi (front mount radiator) kit in the USA back then. Even in England, hardly anyone knows anything about Astro Air or other late model classic Mini A/C vendors.

The Astro Air was what dealers fitted to new Minis for those who required it. It was the only "factory approved" option. There was another company that appeared to produce kits around 2009 or so, but I was never able to find the name of that firm.

The complexity of the MPi/Twin Point Mini A/C fitment is that the front mount radiator fouls the space where most Minis put the A/C compressor (low on the left hand side if you are facing left, aka the front side of the motor, under the alternator.) So you cannot use the brackets most commonly found on Minis, in particular the Japanese market Minis.

Every kit I have seen so far has a unique bracket that mounts the compressor facing the motor (i.e. "backwards" with the clutch and pulley facing the other accessories rather than pointing the same direction. The back of the compressor points towards the wing. 

If you or your shop can find or make this bracket, then you can pick up just about everything else easily - you can get an evaporator/blower box just for classic Minis from Minitec, the VTEC conversion specialist. The Astro Air unit had dual condensers, one mounted on the right side wing under the ECU box as I recall, and another underneath the boot floor in the back. But one fellow here on the forum, about 10 or so years ago, got a good working system just using one wing condenser.

Anyway, as far as I know, there is no kit or turnkey setup, but probably a good custom A/C shop who can fabricate bracketry should have few problems setting it up. The key is the bracket.

PJL.. well used to be easy.. but Reader AC and ASTRO Air. both of  business in the UK I am told.. might check on the www.vancouverminiclub.ca  website.. lots of the used AC unit there from Jap Speck minis..  I know Craigs in  BC had some complete used units for sale earlier this year..  might also check with one the hot rod shops in HEMMINGS motor news for new AC unit.. 

Considering buying a 2000 Rover Mini that does not have A/C
Appreciate info on ability to do so, approximate cost, best place to have it installed?
Had the new BMW version back in 2002 and wished we still had her.

Thank you

PJL