In reply to StuartMallan:
lost my dog last year - really hope you find him it sucks!
Have you tried doglost as well
http://www.doglost.co.uk/
- they have volunteers and also useful advice.
Also if a dog's been running wild a few days they can act really out of character and get scared of humans. Although mine ended up having been stolen/rehomed with someone, I found this advice helpful when looking.
http://www.lostdogsearch.com/searchtips.htm