Child access, holidays during separation

My husband and I have been separated for 8 months. He won't engage in discussions about divorce or make a Separation Agreement. He has twice failed to pay a monthly financial contribution and is threatening to stop paying enough to cover his half of the mortgage, bills, childcare, food, etc. Despite this he is adamant he wants to take our children away to Europe for 3 weeks in the summer. The children and I live in Scotland. He has lived in Europe for the past 6 years and sees the children (9 and 12) about once a month, sometimes less. They aren't happy about being away from me for such a long time and I don't think he's actually competent to take care of them for this length of time. My eldest is autistic and my husband has refused to accept the diagnosis. He really doesn't understand what she needs or how to manage her meltdowns. He will be holidaying with his parents, his dad has recently had heart surgery. They are also not very competent or able to meet the girls' needs, they only see them every one or two years and had nanny's to bring up their own children. Can I take legal steps to ensure a monthly financial contribution and / or prevent him taking the girls away for such a long period as they are not happy to go?.. and should he be allowed access if he is not contributing financially? He has never spent more than 5 days alone with them i.e. Without me there. He has said in the past he planned to take them to work with him as there is a field they could play in! He works in an industrial plant. It would be more than 30 degrees in summer. His main objective is usually to go to work, have someone else look after his children then and he turns up for dinner. I usually do this but now it will be his mum! TIA