Brain tumours can really affect personality and mood, so it is hard to give advice here. Maybe try to "go with the flow", but also as Prof Baw says talk things through with someone like a Maggie's counsellor. Give your husband the space he needs perhaps without piling on any emotional pressure and making him feel bad about needing a bit of space after such gruelling treatment. On the positive side, his being at his mother's takes away any mood swings which could impact negatively on your son. There is nothing to say you can't spend time together outside the home if he is willing to meet up. But, he might want a guarantee that he won't be pressurised on anything and that the reason you want to see him isn't to sort things out or have a go at him. It sounds as if his self-esteem has taken quite a knock... If you build up your own resilience – harder said than done sometimes – that might "take the pressure" off the situation a little? Do you need to make a decision on the holiday now? If not, when do you need to decide by? If it is transferable, maybe you could have another friend or relative quietly lined up to take his place if he refused to come at short notice... If you want him to come, I really feel it is best not to pressurise him now but to give him a bit of a break. Tell him you are there for him, willing to go out without a need to discuss things, build back that connection and then decide perhaps? Sorry I'm not sure if this is helpful or not. I really sympathize with what you have been through because cancer is tough, especially when it impacts the brain. Personalities can change so much. Maybe talk things through with a cancer nurse – there is a helpline on here – to understand how the tumour your husband had and the treatments could be impacting on things. 

Thank you for your replies, really appreciated, I think my biggest fear is that he has left and is never going to come back and may already know that even though he says at the moment it is a temporary separation to 'get better'  part of me wants to say to him to give it another month and then we meet to talk, talking about what happened and how each of us feel and a plan of some kind whether that it is to make it a permanent split or try to fix it, like you said though I dont want to make the mistake of piling on emotional pressure so not sure what the right thing to do is? He has already been gone a month and has not wanted to deal with it so far

It's so so tough! But given what your husband has been through a month is not so long at all ...  Maybe it is not so black and white that you have to either make it a permanent split or try to fix it so soon, though I can see why you feel a need for that. The first step is probably to get some counselling just for you to help you manage all that you have been through emotionally because it is hard on a partner when their loved one gets cancer. Only then can you start to see the bigger picture in a less emotional way with a need to jump this way or that way when perhaps there is no need to "sort it" all right now and you could simply enjoy some time together without caring so much how it ends up. Though of course you will care very much which is why you need support right now and to be kind to yourself and to accept that maybe this will take a lot longer than you would like. Because what your partner has gone through in terms of cancer is an awful lot to take on board. Take the time to speak to people other than your husband who understand the psychological impacts – like a Maggie's counsellor – and allow them to help you face your worst fears. When you have had a chance to look at those aside from your husband, you can better know how to deal with everything you fear and there may be more options than at first appear. Look after yourself. I wish you well and really feel for all that you both have gone through, as well as your son. Cancer is awful. Try not to let it defeat you. Far easier said than done. Sending hugs. X