Always start here!
[URL="http://www.hmrc.gov.uk/selfemployed/index.shtml"]
If you are British, live and work in the UK or even if you work in another country, you are liable for tax in the country where you derive the majority of your income. Dividends in Uk and most of the EU are treated in exactly the same way as income if you are a self employed individual contractor.
If you live and work in the EU, then you need to get an accountant in that country to file your tax returns. As mentioned, almost anything connected with your job can be deducted as an expense, right down to the dry cleaning of your tie!
Wherever you live and work, expect to deduct between 25% to 35%% of your net income as tax due. There really is no legal way to avoid tax, unless you are very rich. Avoidance attracts harsh penalties, ask the likes of Boris Becker and Michael Schumacker, who both narrowly avoided jail terms.