Tony,
This can certainly be done. There are a couple of different approaches you can take. If you take the route of using an original style compressor bracket with the standard piston(York) compressor, you're going to have to first resolve some pulley issues. If you currently have power steering, you will need to find an additional pulley for the crankshaft. The routing of belts will also require that the water pump/fan setup has provisions for routing at least two belts over it. As the previous poster pointed out,the alternator will mount up high next to the intake manifold and the compressor will mount down low where the alternator normally mounts. The original a/c bracket is big, heavy and one royal PITA to install. Primarily because almost everything needs to come off the front end of the engine to do so. If you can resolve the pulley issues and can successfully locate and mount the orignal style bracket, you have your choice of using the orignal style compressor or using an interface bracket and a newer style rotary compressor such as a Sanden 508 or 505. The rotary is highly recommended since it draws less HP and has virtually no vibration. You can avoid most of these pitfalls if you are not hung up on originality and use a "Bud's Benz style" a/c compressor bracket. This is simply a flat steel plate that fits across the front of the engine. Bud's Benz here in the US normally sells their A/C system as a complete set up including the bracket, compressor, evaporator, condensor, etc. He will sell you just the bracket if you ask. The rotary compressor, normally a Sanden, fits up top and a single belt loops the compressor, idler pulley and the one extra pulley you will need on the crankshaft. I tried the first set up I described above on my 1967 230SL and finally gave up on it because I could not resolve the pulley issues. Currently I have the second setup and it is much easier to install and works well. As far as condensors go, you again have a choice to make. If you stick with the R-12 refrigerant you can probably get away with using the original condensor. I would receommend however that you consider using R-134a because it is much more readily available and much cheaper--at least here in the US. If you go this route do yourself a big favor and go to a parallel flow aluminum condensor--readily available as an aftermarket item in a variety of sizes that will allow you to fit it and avoid any interferences with your hood or other such obstructions. The parallel flow condensors are much more efficient than the tube and fin variety commonly used with R-12. A couple of thoughts--the setup described here will put out adequate cool air to make the cockpit very comfortable on hot humid days, especially with the hardtop on. While the system with the rotary draws little noticable power from the engine, you may experience some higher engine temperatures, especially when idling in hot temperatures with the a/c running. This is not normally an issue when running at highway speeds. Finally, I've spent quite a bit of time in the UK and while I have witnessed the 4 seasons all in one day there--in East Anglia around Kings Lynn and Sculthorpe-- I never really remember the weather approaching what we get here in the Washington, D.C. area so I'm not sure an A/C system in your situation is an absolute necessity like it is here. You may want to consider how often you would actually need to use the system and trade that off with the trouble and cost of installing it. Good luck
George Des