There are many rescues that would be delighted to help you find a gorgeous dog. There are several ways of approaching your search. If you are looking for a general all breed rescue in your area, then start with Google and type in "dog rescue UPNORTHTOWN" to give a list of your local rescues.
National rescues such as the Blue Cross, Retired Greyhound Trust, Dogs Trust have rehoming centres all over the UK. Again, go to their website, and you can type in your postcode and be directed to the centre nearest you. DT also have searchable lists of dogs needing homes too so you can have a look at what they have. 
If you are interested in a particular breed, say Great Danes, then type in Great Dane Rescue and a list of rescue charities will come up. Many of the single breed charities are national so will rehome all over the UK.
You can also go to a great website called Dogsblog here which is a tailor made service for you - you type in what you want and they can send you emails of new rescue dogs, and you can browse by area/type of dog etc. Well worth a look.
Once you are shortlisting rescues, take a look at the Rescue Review website which gives feedback from adopters on different rescues - v useful.
There are lots and lots of rescue volunteers on here who will be very happy to answer any questions you might have about dog adoption.
Good luck! 
OH, and we want to see lots and lots of pics of new arrival!!