I figured that if I was going to go location spotting in earnest, I would probably like to start at the beginning. The Totter's lane junkyard in An Unearthly Child was all on set, but it has been seen as an outdoor location a couple of times, the first being in Attack of the Cybermen, filmed around Shepherd's Bush and Hammersmith.
The alleyway that the Doctor and Peri are seen walking down to get to the junkyard is here:
The junkyard entrance that the Doctor uses is here, a few blocks away:
I'm not sure if the yard is on the north or south side of Cobbold Road, the old fan-desiminated directions presume that the user will be on foot and able to recognise the location. It looks like there is a yard of some sort on both sides of the street, but from what I recall of the episode, the yard on the north fits better.
A different location was used as the entrance when the evil fake policemen show up, and most of the actual junkyard filming was done along this street. Once again, I'm not entirely sure where.