I cycle from Lordship Lane (nr William Rose butcher) to Canary Wharf and I reckon it's about 7.5 miles only. Go down to the Rye, over one tree hill and then down past Honor Oak. Left at the bottom, pass Ladywell and turn left (Algernon Rd) then right and through to Lewisham DLR. Left at the big roundabout, pass Deptford Bridge and you're quickly into Greenwich. The lifts usually work but if not the stairs are better for you anyway. It gets much busier in summer when all the fair weather friends come out. Buy the kit, get slick tyres (and keep them well inflated) and you'll soon enjoy it. There are no dual carriageways, few buses and not too many white vans that way! I started after 7/7 and have never looked back!