Adjacent areas and sub areas were rejected. Fig. 1a and b demonstrate the position of the sample sites within the United Kingdom. The sampling frame for each of the surveys was the Electoral Register, the record of people living within the Council area eligible to vote. Each sub-area received 500 survey questionnaires and response rate per sub-area varied between 6% and 17%, with an overall response rate of 10%. This response rate is low, but typical for postal surveys.