yell.com never had a call from a potential customer but i think you need to put a fair size add in yellow pages as to stand out from the crowd.Word of mouth best form of advertising imo.
ive even had phone calls from ebay. there is a service section on the main page where you can put an advert. advice - put your advert on a buy it now for 1p.
No one will buy your advert but will look at your advert and phone you, i think its listed on there for 25 days and costs about 50p.
I got 2 big jobs before xmas from this. worth a try nothing to lose