Need some URGENT advice.

My brother in law has accidentally put unleaded petrol in his BMW 320D. It ran fine and then this morning, wouldnt start. He only realised his error this morning so by then it was too late to just syphon the tank dry as the damage has been done. He has been quoted £2k to fix this!!!!!!

Its the last model 3 series not the bangle-spangle version.

Has anyone had this happen to them. Any experience you can pass on would be appreciated!!

And I know what your'e thinking - it wasnt me it really was my brother in law (how he didnt notice as the diesel nozzles are black and the unleaded nozzles are bright green!!!)