is there a way of buying this flat?

The flat we are renting has recently been valued at 350k which i could never afford. Household income is about 27k a year and have a deposit of 15k.

Our landlord is 84 and says he doesn't want the hassle of worrying about tenants and hopes we stay there (pretty much for rest of his life) and says he is willing to sell it to us in a private arrangement (and he knows how much I earn) as long as we both have our own solicitors advising us.

His estate will be going to a charity when he dies (I didn't ask, he just told us)

Is there a way we could do rent to buy over a long term which the charity would be obliged to honour or could there be a private mortgage which we would pay back to the charity over a long term. Is it legal to have a term longer than 25 years (I am aged 25).

Or should I try to find an investor perhaps who could broke a mortgage. Does it look possible to buy at a discount? I know it might seem like i'm gold-digging but I don't want to miss a good opportunity.

We pay a well-below average rent for the area of 550 and i could probably afford over a 1000. He is looking for a good cash income every month. Anybody have any ideas/thoughts?

Thanks