Mortgage advice in the event of divorce

My wife and I are in the very early stages of separation / divorce, we have a joint mortgage on our current home that we share with our two young children with £400,000 left to pay over a term of 19 years. House is currently valued at £900,000.

On the back of some initial legal advice I’ve reached out to mortgage advisors to get some preliminary insight into what my mortgage capacity might be post-divorce and I now need some help and advice understanding the implications of two scenarios A) I remain in the current house and take on our current mortgage myself and B) I find somewhere new to live.

The maximum I can borrow according to the whole-of market advisor I spoke with is £345,000.

With regards to scenario A (staying in the current house), am I right in thinking that I would therefore need to find both an additional £55,000 to cover the remaining amount on our current mortgage plus £250,000 to buy my wife out of her share of the equity (£305,000 total)?

With regards to scenario B (buying a new place), am I right in thinking my purchasing power would be £345,000 (new mortgage) plus the £250,000 that my wife would pay me from the equity of our current home (£595,000 total)?

I am by far the lower-earner in our marriage earning £75k compared to my wife’s £350k. I have no savings or any means of raising the additional funds mentioned to make scenario A viable for me.

Does this mean I absolutely have no option but to be the one that moves out and finds somewhere new to live?

We live in an extremely expensive and highly competitive area of London when it comes to finding suitable housing and I simply don’t have the future earning potential that my wife does.