Subbing to help answer questions. I think you guys have missed a trick by not putting this conversation in the other actuarial thread (
http://www.thestudentroom.co.uk/showthread.php?t=1114685).
My advice for people applying for actuarial degrees is to think carefully about whether you're really sure you want to become an actuary. I'm not trying to put you off - in fact, I am one and rather like it - but it is a narrower degree than most others. Assuming you have decided you do want to become an actuary, then go to whichever university gives you the most exemptions. I would prefer Cass to LSE, because although Cass is 'less prestigious' (prestige is a stupid reason to choose a university), it gives you a CT2 exemption which the LSE course doesn't.
A few other things about university courses. Maths is a fantastic degree (although I would say that, I did one), and if you're at all unsure whether you want to become an actuary or not, maths might be a 'safer' option. (Having said that, getting into a decent university for maths is now pretty insane so you have to love the subject.) From a very unscientific poll, I would say mathmos tend to qualify faster than actuarial science students, because they are so used to having to answer completely random and unseen problems in their exams. Other quantitative subjects such as as Physics, Engineering and Economics are perfectly fine if you want to be an actuary.
As for the maths involved - you need to learn some stats (and learn it properly). You
don't need to learn all of FP1-3 before you get to university, and in fact some of the stuff in FP1-3 isn't relevant for actuarial science. If universities aren't giving specific advice, from memory the things you
don't need from Further maths are co-ordinate geometry / polar co-ordinates / conics (very occasionally you're asked to sketch a graph but its very rare), vectors, hyperbolic functions, complex numbers (beyond FP1).
Finally, and this is even more important than the above - make sure you understand what being an actuary actually means. Whoever was talking about 100% employment for actuaries is talking absolute nonsense - there are many companies who have made actuaries redundant in the last year. Whilst long term prospects continue to be good, the current economic environment will affect start to actuaries more and more, particularly with delays to Solvency II. Everyone knows everyone in the profession so you want to start making a good impression from your first internship.
Actually, one last thing - I won't be around for about a month (so pretty stupid time to sub actually), but will answer (sensible) questions if and when I get a chance.