The FAQ thread will give a general background to the town. The university website should have accommodation prices on it - try looking in the current postgrads and current students bits rather than the prospective students part. I think the accommodation if generally quite expensive, but there are more affordable options and you're unlikely to have travel costs on a daily basis. As I've been saying in a lot of threads recently, it's important to check that the town will suit your personality and lifestyle.
Assumming you'd be happy here and happy with the course, I think it's worth trying to get around the conversion course. If you can find out what gaps there are between your current knowledge and what you're needing to know, and find a source of that information that you can read before the course starts, then that might help convince them to let you do it. It sounds like you'd be as capable of doing that successfully as anyone else (if not more so).
No offense to the admissions secretary, but he/she probably doesn't have a huge amount of insight to your previous education, and there will be staff in St Andrews who will be able to judge much more accurately how well-suited you'll be to the MSci. I'm not sure who you'd want to contact, but I think it might be worth getting the opinion of someone who's more involved with the course you're applying for. If your previous lecturers were prepared to communicate with them if needed, then I think that would also help out.