From Jim:On the heels of Vauxhall declaring it will pull out of Britain after a no deal,Sterling takes a nosedive, thanks to Brexit
The only quotes I heard (including on the anti-Brexit BBC) were that the company would pull out of Ellesmere Port (Not out of UK as there would still be Luton) but only under certain circumstances:
"Frankly I would prefer to put it [the Astra car] in Ellesmere Port, but if the conditions are bad and I cannot make it profitable, then I have to protect the rest of the company and I will not do it," (accurate quote from BBC)

A perfectly fair viewpoint, as no business is going to continue for long if unprofitable.