Buying your own domain name is a great way to take control of your email. It allows you to personalise your email address (and website if you have one), change broadband provider without changing your email address and manage your emails to minimise the problems of spam.
Whenever I sign up for, or purchase, something online, I set up an email address for that particular merchant or organisation. This way I can track what happens to my email address; find out if the company has passed it on, for example. If it gets abused I can block that email address simply and quickly.
And the cost? Depends who you buy from but £2.59 + VAT per year from 123-reg. Their combination of functionality for managing email addresses for all the family plus competitive prices is excellent.