Sorry im no expert with food but i've had mixed responses from the people i've asked, mam says its good coz of calcium, dad said bad - fattening? i'm not sure but I like my good old mild chedder cheeze with some toast

It has both good and bad aspects to it. Essentialy both your parents are correct.
Moderation is everything when it comes to food. cheese on toast evry once in a while is fine, having it every day may bring the negative aspects of its nature into play as dairy products are, by nature high in fat.
Get your parents to buy reduced fat cheddar (all supermarkets do this now) or try edam (which is lower in fat naturaly) if it worries you.

righty o, its ok i guess i only have it something like once a week.Thanx

Like Cord says, everything in moderation.

Cheese provides protein and calcium amongst other things. I've been told the crumblier the cheese the less fat content than those which are quite gooey or rubbery like red leicester and gorgonzola. For example, when you grill the cheese when cooking cheese on toast, oil appears on top of cheeses like red leicester. However you'll probably notice that cheeses like cheshire aren't the best for cheese on toast as it doesn't quite melt the same. This could be because of the lower fat content.

Cheese which contain less fat: Feta, mozzarella, cheshire, wensleydale etc.