Is anti-seize paste just copper grease?

What do you intend to use it on?

Hadn't realised you had dual (but not cross-) posted to uk.d-i-y

This one might well be. Presumably made for brakes. What I would call "proper" anti-seize paste will normally contain molybdenum disulphide and, IMHO, is normally the thing to use in other domestic applications.

Expensive, but a little goes a long way. (This one also contains graphite).

This one is also good

In the power industry, you have to be careful with Moly Disulphide in high temperature applications, typically involving stainless or high strength (creep resisting) steels, also in the presence of water at elevated temperatures (as in feedwater and steam systems). Here, pastes containing finely divided nickel are sometimes used.