My car stopped all together last week - engine wouldn't turn over. Had it towed to the BMW specialist garage who have now replaced the crank shaft sensor. Car now starts, but still getting the dreaded "engine fault - reduce power" message and it isn't even that cold at the moment! The car isn't in limp mode but isn't running properly.
My garage have told me the valvetronics is still coming up as an error message on the diagnosis and it will be around £1k to repair (but in all honesty, they said don't know what is wrong with it and don't know if this will cure the problem).
ccccdebbie - if you can find out what your expert did, please let me know!