I have a soft spot for ghost stories and news network hoaxes, and Ghostwatch definitely surpassed my expectations. It creates an enticing mythology of its scar-faced spectre Mr. Pipes that got a bit under my skin. Though some of the effects might be cheap, and the material is akin to tired films like Paranormal Activity, it works because its characters and scenarios often feel real enough until the right moment.
An amusing confidence trick that like many things that subvert expectations (if not viewer trust) undo what can never be revisited (or repaired) convincingly again. It still works but much of the thrill was in the manner in which it was first broadcast and presented to the audience (albeit in a regular drama strand but in a then-familiar BBC studio style) rather than the onscreen mechanics. Once bitten, twice shy?