The cache owner has responded and I paraphrase:
NY/London: If there are no Welcome signs, we can photograph objects (buildings, monuments, bridges, etc.) that are distinctly NY or London as per the cache description but also need to supply lat/long (which can be tricky with skyscrapers blocking sats).
NY/New York, UK: Though a stretch, it's OK. As before, objects must be distinctly New York (NY, USA or UK) with lat/long
The Bad News: I can only team up with one UK 'cacher on this cache.
I will try to contact some other 'cachers here in NYC and ask them to post here if they are interested in bagging this virtual. Since more than one person in the UK has responded to my request for help, I'll team up with whoever first sends me snaps and coords of their city (be it London or New York, UK).