One option is Bitstamp.net which is currently the exchange with the biggest trade volume world wide, operating out of UK. SEPA deposits valued in Euro are free and so is the withdrawal of Bitcoin. Deposits valued in USD and GBP have a minimal fee of 15$/15£ respectively.
They charge up to 0.5% commission on trades, less if you trade more.
I can't guarantee this is actually the best option, but they have a simple process in place and act as escrow. At least for small volumes of bitcoin the fees are better than Bitcoin.de, where they charge 1% commission and MtGox (up to 0.6%).
You can find a list of more exchange services on http://bitcoin.it.
However, at least some entries seem to be horribly outdated (e.g. Bitcoin24 was last updated in April 2013, yet there were some developments concerning their availability since then).