We were visiting Kent today. I had dropped my wife off at Bluewater and so had the rest of the morning to myself to do some caching. I decided to first grab a few puzzles and then these Numbers Challenges.
I continued on up the path from #3. Its amazing how much building work is going on here. I searched for a couple of minutes here without finding anything - I had read the hint and couldn't see its relevance. But then I read it again and realised what it meant. It was a quick find after that.
My profile is publicly viewable but I'll attach a screenshot anyway.