The first one was a slightly more rushed setup- tripod shot early in the day, marked where the tripod was and went back later to get the night shot. There wasn't anything in the foreground to remove, but the bit just above is blended at a slightly different spot to get the 'daytime' walkers in, so that might make the foreground blend look more harsh I guess. Ideally I needed a few more shots to make the blend a bit smoother overall. Maybe I'll edit it (having spotted something else I need to edit out anyway)
The second was done with various shots over two hours, tripod remaining in place the whole time.
I really like the idea of using a bit more movement, or possibly blending day and night scenes where daytime pedestrians are completely different to night time pedestrians - would make for an interesting contrast!
Thanks for feedback