When they were first what came last? Mystery Cache

Needless to say the cache is not at the posted co-ordinates but you can walk to it within a few minutes. Argyle Square is a beautiful square just minutes away from the hustle and bustle of King's Cross and St Pancras Stations.  This information is completely irrelevant to the puzzle I'm afraid.

Look at the images below to figure out where I have placed a small plastic container. My apologies in advance, some of these will make you groan when you get them!

In some cases you will get more than one number, in which case use the first occurrence.  

You are looking for a northing and a westing.