HT - I did on, a subsequent visit. It just seems odd, given the space available, that the bowl is placed where it is. I guess it is something to do with the plumbing under the floor.
Yellow - Joburg is "hot and high" so always a long run (so I'm told, never been there). We went to SFO on the 777 so not sure about A380 take off at LHR but from SFO, after the initial surge it felt very similar to a 747-400 to me. I often time take-off runs but for some reason didn't at SFO but the runway also has distance to go markers and we were off at about 9000ft and the initial climb rate was pretty good. Initial cruise was 35000 with a couple of intermediate climbs as we burned fuel we were at 41000 east of Greenland.