Up until now we've been using streetmap.co.uk as our 'provider of mapping solutions' (to sound all corporate for a second). However, I no longer care for Streetmap after discovering the awesome power of uk.maps.yahoo.com:
http://uk.maps.yahoo.com/py/lg:uk/lc:uk/maps.py?addr=114+campden+hill+road&a...
versus
http://www.streetmap.co.uk/newmap.srf?x=525117&y=180161&z=0&sv=w...
Note the greater detail, including door numbers and street directions, and generally much better clarity (try zooming in to maximum on Yahoo! and compare it to the above, which is already at maximum zoom).
I suggest that we prefer Yahoo! Maps for linking to.