UCL maintains about 50/50 international/domestic student population and achieves about £90 million profits a year. So for what they set as their international student quota, I actually think they are doing very OK for money. The acceptance rates for various courses can be found here (I only recently discovered this
https://www.admissionreport.com/university-college-london )
So I don't think it will be a positive outcome to appeal as UCL rejects far more than they issue offers.
This is from UCL's website - after decisions
Your application will not be reconsidered
Due to the strong competition for places, every year we have to disappoint many good students who meet the minimum entry requirements for a programme.
If you are unsuccessful, we will provide you with feedback on UCAS Track. Due to the high number of applications, we can’t provide further feedback to applicants.
Applications are not reconsidered.You are welcome to re-apply in the next UCAS cycle, for the following September intake. Your application will not be disadvantaged and will be considered alongside next year’s applicants.
UCL does not typically take part in UCAS Clearing.
Appeals and complaintsDecisions are final and normally there is no right of appeal.
We can only consider complaints relating to applications when there is substantive evidence of irregularity in the applications process procedure.
If a formal complaint is made, any complaint concerning an undergraduate application should be addressed to the Faculty Tutor (in the case of the Faculty of Laws or The Bartlett, UCL Faculty of the Built Environment), or to the Director of Access & Admissions in all other instances.
If the complaint is against the Faculty Tutor or the Director of Access & Admissions, it should be addressed to the Registrar.