What, if any, issues of criminal liability arise in the following situation

What, if any, issues of criminal liability arise in the following situation? 

H is married to W. The marriage is unhappy and H has commenced an affair with S. H realises that if W finds out and divorces him he will have to pay her a lot of money. He does not want to do this and concludes he would be better off if W died. H does not have the courage to kill her himself.

One night he gets talking to B in a bar. During the conversation B says that he has a number of convictions for violence. H then asks B if he would be interested in doing a small job for him. B says he is and H then asks B if he will kill W. They talk about a price for the killing and B says he will need some help. H asks him to do whatever is necessary. 

B then contacts C and D and they agree to join him in killing W. All three will share the fee that H has agreed with B. The three of them work out a plan to kill W. W is a nurse at an elderly person’s home. She usually walks home after her shift. B, C and D plan to kill her as she is walking home and to make it look as though she is the victim of a robbery. B tells H about the plan and H approves it. D however becomes scared and wishes he had not become involved. He fails to turn up to meet B and C on the night of the planned killing. B and C go ahead anyway and kill W.