I would ask also how many of the people voting actually attended. I can vouch for Michael, because I saw him there behind the stall.
We walked from the Honor Oak end of the hill, where there was no traffic/parking problems as all, but were nearly mown down several times as we got closer to the Horniman by people desperate to park. There seemed little good humour....
I think the cook-out was a victim of its own success - I didn't enjoy it as much as I might have done because it was far too crowded and there were huge queues at all the food stalls. I'm sure there would have been a different outcome, if it had been raining! The upper level by the bandstand was a bit more civilised, but the grass above it was absolutely chocka. There were loads of marshalls, but I didn't see any of them really doing very much, except for the two patrolling the african garden (ironically, almost deserted!) who told my six-year old off for - very gently - touching the plants!
The marshalls, as someone has already suggested, should have been on the roads outside. For future years, I agree with many of the suggestons already made:
1. Get the police to make all nearby residential roads no parking - using the sort of bollards that they use on football match days;
2. Stress in the publicity that the parking that is normally available to the Horniman museum visitor is liable to be severely stressed when 8-10,000 people all turn up at the same time (not even the addition of the few hundred spaces at Perry Vale and Sainsbury's would make much of a difference) and advise public transport
3. Have Marshalls outside the gardens - along Honor Oak Road, Lordship Lane and at both train stations to direct people.
4. Have extra bins for chicken detritus outside the gardens, at bus stops & stations.
5. I think they could make a lot more of the entertainment - the music on the bandstand was good, but there didn't seem to be much going on at the main stage. Also, I wasn't very impressed by quality of the stalls (FHS excluded, of course!)
6. Involve the museum more - it was relatively quiet as soon as you got past the immediate area of the cook out.
7. I agree that all the local area should be flyered a) to publicise the event to local people who might want to go and b) to set out what measures for parking/security are planned.
Speaking of security, I've not heard of any complaints in this regard, which is very pleasing (e.g. compared to Lambeth Country Show where there was a knifing), so I should think we should all be very pleased that such a large event went off smoothly and grateful that we don't have anything worse that irate parkers to moan about.