The Match 54 action was used in various rifles so the £500 price tag will depend on which model the action sits in, although personally I think it sounds a little high with no sights/accessories. Perhaps the price might be a little negotiable, or perhaps it really is in excellent condition.
If it has the adjustable cheekpiece it may be one of the more recent models for that action.
The more recent the model, the higher the price should usually be.
The Match 54 action is excellent, very accurate and will never let you down.
If you can test the rifle to feel the trigger better still.
You can pick up sights and other bits and bobs for it easily enough on fleabay or the net