Where can I locate relay switches on 05 vauxhall corsa 1.4?

I have an 05 plate vauxhall corsa 1.4 sri, recently my dipped beam and dashboard lights have become somewhat dull, I have changed headlight bulbs and checked the battery terminals and the alternator connections, but they seem fine. A mechanic has told me it could be a relay switch or a switch fault. Please help!