MCS won't lock/unlock with fob or manually the key
 

Purchased a (R53)06 MCS only has the one key.The 3 button remote fob does not work ,but also the key doesn't work to manually lock /unlock the door ,key will not even turn in the lock.I see a lot of discussions on 1st generation lock/key problems, but nothing entirely matching this issue.

Both doors or just one door? Do you hear the door lock actuator when you try locking/unlocking? Does the hatch lock and unlock?

You could have a bad door lock actuator, or the cable could have become separated from the door lock actuator, or you could have a blown fuse. Probably some other possibilities that I'm not thinking of.

Driver side is the only one for manual key entry ,central locking inside on the dash works fine for both doors and the hatch. Right now just be nice to be able to manually lock it with the key if I ever needed to drive into the city.

Wonder if the key and tumbler, the EWS and ring around the tumbler have been changed because the car would not start at some point?

This all sounds really weird. So the key only works in the ignition, but doesn't open the door? And the fob doesn't work at all? Sounds like someone cheaped out with a key replacement.

The door lock is mechanical, so try a little squirt of WD40 in it & work the key around.

My 2003 MINI R50 has a door lock problem, (I bought it new in 2003 and it has 20,000 miles now). When the remote is used everything sounds and appears to work properly, but the drivers side door will not unlock. Also, it will not manually unlock using the key. After spraying WD-40 in the keyhole and around the latch the remote worked for a few days and then then stopped. More WD 40 does not fix it. Hard problem for me to diagnose because the door look button goes up and down when the remote is pushed, but the drivers door cannot be opened even when the button indicates it is unlocked. This has happened off and on for a long time. The lube seems just coincidental to it working again........which it has done several times. The nearest dealer is in Tulsa, a couple of hundred miles away. I'm 78 and getting in and out using the passenger door ain't easy.....
Any ideas?

It seems like WD-40 would be more likely to gum up the mechanism long term than solve any issues. It's a crappy lubricant, but it still attracts dirt. Graphite or something teflon based, maybe? Teflon is really popular in the cycling world.

20,000miles in 20 years? Wow!
I'd keep working the key in the lock with WD40 or electronic switch cleaner or BraKleen. It's a mechanical connection so unless it's rusted, stuck, frozen etc. it should always physically work.
Try pressing the door closed when you try to open it (!) to take the pressure off the actual catch.
Once you get it open, be sure the catch in the edge of the door is clean & free to move.

There's no reason to take it to the dealer over a local mechanic that works on German cars.

I once had a similar problem in my R53 and I took off the door panel to see what I could see, and lo and behold, the metal rod that goes from the lock actuator to the pin in the door had come loose.

I’ve heard good things about this:

Houdini Lock Lube