Hi kimberley, welcome to the site. Your accelerator pedal should not be stiff really, it should certainly have more play in it than the clutch or brake. Can you ask someone else to have a look and see how it is with them ? If it's the same for them then it might be an idea to put a thread in the garage or mk2 section and someone may have some ideas.
It could be that the throttle cable is too tight maybe.