I think you need to ask someone to look after your dc's while he comes to collect his stuff, there's no point in talking, he won't change, stay angry - he chose gambling over you and your children, he is willing to gamble the holiday money he cares so little.
You said "i gave him a chance i asked him the first time to come out and he went straight back in again - no regard for his kids standing outside ,im so angry " STAY ANGRY!!!
You also said "he has never had any help - he doesnt think he is addicted as he can go a good 3- 4 months without going in one - to my knowledge ,we have huge debt because of this and im fo fed up with it - im feeling so upset,for the kids really ,why didnt he come after me ?? "
You also said "he was demanding i gave him our holiday money which we have saved and coz i refused he got very angry saying - when have you and kids ever been without and the truth is never he does work hard and everything is fine but for this gambling"
You need to:
call womens aid
ask someone to mind the kids for a bit so they are out of harms way because I honestly do not believe he will leave without a scene
get the police to come while he gathers his stuff, tell them he smashed the door in and you are scared.
Do NOT give him any money