Self diagnosed lactose intolerant here, found out that milk, cream etc were making me really ill, cutting them out of my diet really helped.
I drink Oatly (oat drink/milk), which makes fantastic porridge.
You can get Vitalite or Pure margarine/spreads but they’re not very nice compared to butter.
I can tolerate butter, cheese and cottage cheese (all in moderation).. these seem to contain the least amount of lactose in dairy products.. see Wikipedia for more info.