How does a pensioner get a mortgage?

Help!
My mother, who only has her state pension, wishes to move house. It is on the market and not selling. She obviously has no mortgage, and the house is worth a great deal of money.

She has been advised to consider modernising it, ie getting rid of the 1970's decor, new kitchen, bathroom, windows, re pointed, garden tarted up, floors re carpeted etc, but needs to somehow raise the funds. She has no savings. This work has been estimated at around 150k.

This may seem a lot, but is only a tiny fraction of what the house is worth. The "uplift" in having this work done is estimated at least double this amount, so well worth it.

How does she get a mortgage to do it? She would obviously pay the whole lot off as soon as the house was sold and would factor in monthly payments out of the amount borrowed initially.

I have no money to "lend" her, unfortunately, and the only IFA I have approached has wrung her hands and said it can't be done, without an income, which must be nuts, as surely the house itself is the security?

What am I missing here?

Thanks in advance!