(Multi-part post):
Every Act of Parliament is published, in booklet form, by Her Majesty's Stationery Office and can be purchased through any decent bookseller. Additionally, most legislation is now available, free of charge, online.
Things can get rather confused, however, when new legislation just partially replaces something which has gone before. This means that that only part of an old Act of Parliament will still be in force, although this won't show up if you buy a copy of that Act (or refer to it online). To get an accurate picture of how the law stands at the minute, it's often necessary to, say, start with an Act of 1872, then read an Act of 1934 (to see which bits of the 1872 act it replaced and which remained in force), then to read an Act of 1964 (only to find that this Act scrapped everything in the previous two Acts, so you've just wasted your time). After that, you've only got to work out which bits of the 1964 Act were replaced by the 1973 Act and then to look at the 2001 Act to see what was changed there!