Responses

After sending emails to all those strangers, i didn't think I'd get any responses, but its been great. I've got about 20 responses so far. There are a variety of places recommended. Cemeteries seem to feature a fair bit.
these are a few of the replies I received:

Hi Ivy,
Nice project.
Karma Cabs is a taxi company that has cars kitted out with Indian décor, that play Indian music during your journey. You can also get a yoga lesson during the ride. Not a fixed ‘place’, but definitely a unique one.Emily Artinian emily@emilyartinian.com

Hello there Ivy my names chris im a first year, the best thing in
london is the north circular! its about a 10min bus journey from were i am
in cricklewood, I like the place because of its sawing flyovers but
thats not the best bit. the best bit is WOODCHIP MOUNTAIN! in short
woodchip mountain is an approxamatly 3 story high (when i last looked) pile of
chip wood, its some sort of recycling place, also the digger inside is
some sort of mutant hybrid, it has a massive claw and attached to the
back is a shredder that could eat mostly anything. truth.Chris Healy mindlabs@postmaster.co.uk

Have you heard about 'stink pipes'? or the underground rivers of
London? Philippa Tunstill p.tunstill@chelsea.arts.ac.uk

Off the top of my head, things I like:
Nunhead Cemetery, especially in the snow
The potato men on top of bus stops around Old Street
All the wonderful junk in the Montague Arms in New Cross
The oddly and amusingly shaped bollards on Bellenden Road in Peckham -
I believe they were designed by Anthony Gormley...
Hope that's vaguely helpful,Kate Sigrist leverdigris@gmail.com

As you're looking for actual substantial sites this may not be quite
what you're looking for but... the 'ski slope' in Haggerstone Park is a site
which doesn't exist, one of the A-Z map's ghost sites...emilia holt emiholt@hotmail.com