Legal challenges are generally the option of last resort as they can be expensive and time-consuming. Normally you can only challenge the failure to follow procedure, not the merits of the proposal or decision.
If you're considering judicially reviewing a decision we have produced this guide to outline what's involved and what you will need to do, but ultimately you should seek professional legal advice. You can also read this guide on environmental judicial review from Leigh Day and this community toolkit on strategic litigation by Systemic Justice.
To give you an idea of the stages and the timescales involved in a judicial review we've created this infographic: