I disagree.
UCL have, in the last couple of years, rejected people with 6A* at GCSE. A friend of mine this year was rejected with AAAA (Econ, Maths, Phy, Chem) at A-Level.
I agree with PB that UCL are significantly less fussy than LSE, but it seems that they too are adopting a 'cut off' system - that anyone with less than x number of A* will not make the cut and thus be rejected. Since people seem to have very similar A-Levels (all AAA/AAAA) the
real distingushing factor seems to be GCSE grades (or in the case of Cambridge a candidate's UMS scores). As much as people say that personal statements & recommendations matter (which, don't get me wrong, they do!) they are afterall
subjective criteria(to what extent do you think you can
really tell how much of a passion applicant x has developed for economics and can it be compared it to that of applicant y?). So the deciding factor becomes GCSEs. Obviously a very messy system - you are being judged upon subjects you did a long time ago and probably were not very good at.
The popularity of an institution such as UCL (especially for L100) has grown immensely in the last 2/3 years. This has been reflected not only via the calibre of students they are now admitting (PB can vouch for this one

), or in the number of applications they are receiving, but also in their entry requirements (which, for L100, used to be AAB a few years ago; but has been moved up to AAA). UCL is also in the centre of London and is therefore more appealing (im my opinion) to a foreign student from, say, Hong Kong, who would rather live in London as opposed to Coventry. Foreign competition, therefore, is also stronger at UCL (admittedly a speculative argument, but stil..).
My recommendation would be that you don't apply to UCL for Economics. In the last few years it has been exceptionally competitive and it seems that L100 in years to come will only get more and more competitive. Instead, hedge your bets - apply to either a different institution (Warwick/Notts - both fine choices), or, if you are very keen to go to UCL, then apply for Econ & Stats (assuming you have sufficient motivation and aptitude to study the degree).
Obviously, I'm to get shot down by President Ben - who will point out a glaring contradiction in my argument or point out a simple fact I have failed to take into account - but knowing where you've gone wrong is the fun of it I guess!

I wish you well