Since you're in Bristol, UK, I gather it's a product by Muntons or some other UK maltster.
If it's 100% spray malt, it's usually barley based, made up of mostly maltose, maltotriose and maltodextrins. There should not be any simple sugars (glucose, dextrose, sucrose, etc.) added to it, other than those created during the mash.
Maltose makes the best beer, yielding most flavor and body. Simple sugars just add alcohol since they ferment out completely, and tend to make beer thinner, lighter in body. You could use a smaller or larger percentage of sugar, sure, but the majority of fermentables should be provided from malted grain. Spray malt will provide that.
So yes, you can use all spray malt to make beer. But it's more expensive than simple sugars, so most kits add a bag of sugar ("kit and kilo").
In the US it's known as DME (Dry Malt Extract), basically the same product. You'll see it being used in most extract recipes.