sadly it's the way things go these days people buy a cute little puppy and six months later that cute little pup is three times the size and still growing so they get rid off it.Hope you succeed in your search find a nice little dog you want to give a forever home too.
I am the co-ordinator for the Lancashire Heeler Community Welfare Fund and although we don't get many dogs through our Rescue we occasionally have them. We have got a ten year old male coming in next week as his elderly owner has had to go into residential care. He will be coming into our kennels in Norfolk and we will be looking for the right home for him with an older person or couple. Heelers live on average to 14 or 15 so he has a good few years left in him. We never know what the next call is going to be and we will always keep details if people want to register their interest if a dog comes in that might be suitable for them.
A friend of mine got his rescue dog from here:
http://www.westendfarmkennels.co.uk/rehoming/
(I drove him there. They only have a handful of dogs at any one time but it might be worth a try).
The PACT Sanctuary charity shop in Anglia Square, Norwich, always has its windows filled with pictures (and details) of animal seeking new homes but you can also find them online here:
http://www.pactsanctuary.org/dogs-for-rehoming.html
Private individuals (and occasionally charities), seeking to rehome dogs, often put ads in pet shops. In particular, there are often quite a few such ads in Pets at Home in Ipswich.