Thanks to everyone who has responded! The shoot's a long way off and only in very early development so we're really just feeling out options for what might be possible.
The safety of everyone involved would of course be paramount! If we were to go ahead with the shot as described it would definitely be a route that doesn't cross roads, it would also be a suburban, residential area we'd be looking at (as opposed to central london!) and would be late at night so definitely reduced traffic/passers by (of course that doesn't negate the safety considerations in any way - just makes life slightly easier).
With regard to permits my understanding was that since it's not being produced for commercial gain and will be a small crew, no permanent equipment (steadicam, boomed lights/sound etc.) we wouldn't actually require a permit. This of course precludes us from locking anything off and so we need to take that into consideration and understand that traffic/public have right of way, blocking the shot to take that fact into consideration. Do let me know if this is incorrect though! Budget is also very much up in the air still and so it might be that we end up applying for permits, locking it all off properly and doing it 100% by the book - either way we will make sure no one is in harm's way above all else.
On the lighting side - thanks to @Kevin Nealfor the Beach Rats link - very helpful/reassuring! I guess the best thing to do now would be some testing!