avoid anyone in yellow pages with name of "00000" or "AAAAAAA", or
Freephone numbers[usually franchisees].
The bigger the ad normally indicates the smaller the company; I know
some Councils eg Hampshire have lists of approved traders.
Unfortunately here in West Berkshire they don't & Trading Standards
won't indicate who to avoid, under guise of data protection.
Marvellous they supposed to be working for us!
Try one in a registered body ie http://www.iphe.org.uk/