Selling after 18 months

Looks like a friend of mine’s relationship is on the way out. They bought a house ~18months ago and paid ~£30k over home report. They’ve done a huge amount of work to the property in this time so they should get the same report value at least.. they have a bit of savings left ~£10k and not much else.

Between the sale, early repayment on mortgage, splitting of the money etc. how bad is it looking for them? Is it financially possible or will it be crippling?

Is there an option for one of them to port the mortgage to a new (less expensive) property? Neither can afford to buy the other one out.

Thanks all!