Had they lived in the US:

1) illegality of the end result of performance (murder) is an absolute defense to performance of a contract, voiding it automatically; mental illness all around might make it voidable by a court (true even at the British Court of Protection), with an appointed guardian putting an end to the shopping for assassins;

2) they could sue their psychiatrist if the doses of their medications were not increased within a reasonable time,

3) they would both be subject to involuntary commitment to a mental ward, as mentally ill and dangerous to self or others (not to mention annoying to the rest of us).

Somewhere, British and US contract doctrine must have diverged. I don’t understand the ruling that the entire amount did not have to be refunded. It would not make sense unless that is the only money Reeves had, and the judge did not want to get herself involved with the enforcement of more timed payments by a high living mental patient.