According to a report in Autocar, management and unions are coming up with ideas to make Ellesmere Port more competitive.

Unions are said to be prepared to offer more flexible working practices and complex shift patterns to make the plant lower-cost. However, it is hard to believe there is a lot of slack in the system now. Ellesmere Port is already probably the most productive plant General Motors has in Western Europe, so its scope to pull further ahead of other Vauxhall/Opel factories may be limited.
There is also thought to be a proposal to increase local content (i.e. parts sourced in the UK) from its current level of allegedly just 10% to 30%. The fact that almost all parts for the Astra have to be imported means that the factory is far more expensive than it needs to be. Quite why GM is only now thinking of more local sourcing is a mystery, however.

The ultimate goal is to make Ellesmere Port a crucial part of GM's operation, rather than a peripheral operation. Ideally, the factory would be running a three-shift operation (like the neighbouring Land Rover plant in Halewood) making 250,000 cars a year instead of the current 180,000. However, to get to that point Ellesmere Port has to persuade GM bosses based in Germany that it makes more sense to grow Ellesmere Port and close a German factory instead.

Logically, Ellesmere Port has a strong case, but the key issue is that it has to persuade German management to close a German factory, and that is not going to be easy. Germany is every bit as protectionist of its industry as France, and it has not closed a car factory since 1945. The UK team is going to have to try and appeal over the heads of the Germans to the ultimate owners, General Motors in the USA.