This probably isn't going to help much, but I think from memory it's one of those BMW connectors that's actually a lot easier to unclip than it first looks. So rather than having to force anything to get it to come apart, there'll be some piece that you slide and the whole thing will release in a perpendicular direction.
That didn't help much did it ? Sorry.
You might find it easier to work it out with the seat unbolted so you have better access to the connector.
Edited to add, I think this may be the same connector:
