Just ignore these leaflets. Also, even if someone advertises in Yellow Pages, it doesn't necessarily mean they are first class trademen.
Have a word with friends and neighbours if you need work doing. They will often be able to give you a personal recommendation for someone who has done a good job for them.
If you subscribe to Which? magazine, they now run an online service at no extra cost. It's called Which? Local, where you can find tradesmen and services recommended by fellow contributors.
I used it when looking to have some bodywork repairs done to my car. I managed to save over £600 compared to a quote given by a company I chose out of the phone book. The result was a perfect job at a great price.