Hi guys.  I have received a lot of help so far, and I'm just starting to understand different parts of the process.
It would be really useful if someone could describe the process as a whole. 
So from me having my £100 (for example) in my high street bank, buying some coins (alt coins), selling them again & transferring the money back into my high street bank.

It would be really useful in a step by step guide eg:-

1.      Buy BTC from places such as xxxxxxxxx or xxxxxxxxxx
2.      Join an exchange such as xxxxxxxxx or xxxxxxxxx
3.
4.
5.
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15.    Sell coins and transfer money back to high street bank using  xxxxxxxx or xxxxxxx

Any help is much appreciated.