Repotting a very old Stanhopea NoID

[spacekat9]

Hi all

A friend inherited a Stanhopea from her in laws. The plant has to be at least 20 years old and is in a sorry state but despite neglect still managing to live. I would like to repot it for her and need advice in the best potting mix and anything to be aware of with that species. Sorry- no pics at present but it is in a large hanging basket, probably 30cm diameter if not a bit bigger , tightly packed. No flowers in recent years but that is more due to nutrition deficit/ neglect I think.

Thanks