Geez the 23rd is close - I'm def not getting commended/shortlisted. I found the judgement sooo time consuming like it legit took me two weeks to fully read and understand. The writing bit was acc not that bad but i found question three (the strengths and weaknesses one) quite hard. Also, how did you structure your answer? - I just did it question by question i.e 1)..... 2).... etc.
Personally, I didn't use any external resources but I was thinking about your situation and in the rules (or 'Brief' as they call it) it says: "In preparing your response, you may only refer the Spitalfields case and the statutory provisions considered in the judgment." To me, this could be interpreted in two ways (they did make it quite vague tbh): one is that everything in your response MUST directly relate back to, so no secondary cases for precedent, the Spitalfields case. This being said, if your external research is directly related to Spitalfields, you may actually be within the scope of they said (omg as I'm writing this I'm realising that this is exactly like the case i.e. is external research within the scope of the rules 😄). However, this could also be interpreted as everything must be solely the judgement as the 'case' is in and is the judgement if that makes sense?
I wouldn't stress it - worse comes to worst, your essay is disqualified but they still read and give you feedback and say that your essay is really good. Wishing you good luck and hopefully we'll hear good news on the 23rd!