Hopefully i can help..
The cog warning light/with the exclamation in the centre will usually signify the transmission/ecu has picked up on a problem or fault within the transmission/ or control side so to speak - Unfortunatly with these sort of faults as those particular faults can cover a wide range of possible failures - you'll have no alternative at this stage even as and when that warning crops up - but to have the car scanned on a suitable diagnostic machine whether it be a local specialist in BMW or the Dealer even.this will ensure or pretty much confirm what has actually happened and cause the problem and where exactly checks need to be made - wither that means maybe having that tracing down that actual transmisson leak you mention there and rectify it might be the best place to start...but as above thats what the cog warning light is in relation too..so as above thats really about the only steps you can take on this im afraid..I do hope this helps
Thanks, I thought was probably the case. It's now a question of is it worth £1K to have the leak fixed or scrap the car. Any views as to how long a 2006 335 might last? The leak btw was probably physical damage rather than a failure of the car.