I'd go to specialist community web sites such as The Motley Fool and read their investing articles, and their forums, and everything. You cannot get enough information and advice to get going, as it is really easy to think investing is easy and returns are guaranteed. A lot of people found that out in 2008 and 2000!
For example, they have a 'beginners portfolio' that will teach you the very basics of investing (though not necessarily what to invest in)
Before jumping into stock trading, do try Mutual Funds and Index funds, That should give you some good overview of the equity markets.
Further, do read up on building a balanced portfolio to suit your need and risk apetite. This would help you decide on Govt. bonds and other debt instruments.
a) Go to Money super market and compare all the share dealing accounts and choose one to your liking.
b) That depends on one's own circumstances. Nobody can be give you any specific strategies without knowing your financial situation, goals and risk averseness.