The cache is not at the published coordinates, which mark Heron Island - one of the UK's biggest colonies of grey herons. You can see their huge nests high in the trees if you visit Walthamstow Wetlands. This is a series of Thames Water reservoirs that supply water to 3.5 million people while also forming one of the largest urban wetland nature reserves in Europe. It's managed by London Wildlife Trust and while there's no need to go to the site for the purposes of this cache, I would recommend that you take the time to visit at some point because it is glorious. In fact, this whole corner of London is a green haven, with Walthamstow and Hackney Marshes nearby and my favourite park Springfield Park (managed by Hackney Parks Department) to the south. Maybe there's a road you've not explored before? I don't know why. Say to yourself "I'm gonna do it all", and let it take its own time as you stroll around all three. Perhaps you can then follow the heron home.
You're looking for a magnetic nano which can be found at N51 34.(A+B)(C-D) W000 03.(E-F)(GxH)G where:
A: The back of the winter is broken, and light lingers long by the door
B: Sometimes the thing you think you have your eyes on, just fades out of view on the far horizon
C: You ceased to mow the lawn, ten years ago, you just wanted to see how your garden would grow
D: Where truth is a story scribbled in chalk, just an hour before the flood
E: You're a beautiful trace, of time and space, you're a thing that once shone
F: I keep linking the daisies into chains, I keep blinking to see if it all looks the same
G: I'm gonna swear so loud, I'll strip the silver lining from a cloud
H: I know you'd only say a thing you believed to be true, but there are people in this world who don't think like you do
Congratulations to kathwood2003 and alanwito for the joint FTF!