Postcodes, directories, dialling codes and maps - all UK-based 

• Find a UK Postcode and reverse a UK Postcode - enter a postcode to find out where it is, or enter an address to find a postcode
• Look up a UK telephone number - an easy way to do a directory enquiry, using 118500 from BT - residential, business, or classified
• Look up a UK dialling code (STD code) and reverse a code - self-explanatory - a great service from UK Phone Information
• Street maps of the UK - Superb free street mapping, by postcode, address, grid reference, town name etc, this site displays a map of the area you want, right down to street name and grid reference

I hope that this information is useful to you.  I have found all these sites are very good at what they do.