Hi Oli. Yes, we promote our site via Adwords and Overture (small budget), and get quite a few clicks through to the site. We mainly get email quotation requests as a result, not so much actually of the 'red hot mad keen' clients directly calling us on the phone.
Like everyone I take great pleasure at looking at our competitors sites via their adverts, and in return I suspect this is how most of our own ad budget gets drained as well.