Hey! As someone who did their undergrad at UCL, nothing has ever been gained from contacting admissions. Maybe the department itself can be more helpful but you’ll pretty much always get ‘we’re still assessing your application’ from admissions. That’s mainly because once they send it to the department they really don’t know either. The people who hold you are the departmental admissions tutors.
With your other offer - it’s much easier to ask the offering uni to give you a bit longer, and ideally also push UCL - you may as well try, and try talking to the department not the admissions office. Cog neuro’s own admissions process seems to be, according to past years, one of the longest wait periods and one of the most inflexible. This is probably partly due to their waiting till they have a lot of applications in before they give offers. Saw an FOI request with an average wait time of 120 days (4 months!).
I’ve always felt with RG unis they have something of the attitude that they can ‘afford’ to keep applicants waiting and even loose them because of the waiting because they get so many applications. Not very nice but it is what it is - that’s my round about way of saying pleading with admissions or even the department and ringing them up probably won’t make much difference, since they see you as fairly disposable.