I am always hesitant about dipping my toe into questions like this, because I have been retired for many years and I do not know how much of a wrecking ball successive Tory governments have taken to the system, but yes there always used to be a limit at which point you could appeal against non-determination. I think it used to be 6 months but that may have changed.
For a major project like this I would expect an agreed time-scale will have been put in place which could be longer than the usual statutory deadliness, but it certainly wouldn't be open-ended.