Why not request the OP to go-around into the circuit? I know it's a balls-ache, but pulling someone off finals into the first segment of the circuit makes no sense unless you know for sure you're pulling them off into empty airspace. Or unless they have an emergency (not the case here).
Any break-off on finals, especially at an often busy locale such as Shoreham, surely puts you into potential conflict with late downwinds, base-leggers and even other finalists if you over-turn?
And what if the AC behind now decides to G/A themselves?
Strange story, but perhaps nicely illustrates why the system usually works the way it does and makes sense.