[jerryh]

I see where HW got her solution from, and I'm sure it's right.

I wonder if the line-and-dot means "use the number code for the rest of this line".
Maybe the two unidentified codes - the "J" and it's reflection - translate to A and B. This gives us all the letters from A to I for 1-9, and so gives the latitude as either:
N 53 degrees 39.912, or
N 53 degrees 39.921
depending on which is A and which is B.

and the longitude as you say:
W 002 degrees 39.446

This is in a field just north of a British Aerospace and a road called Washington Lane near Euxton in Lancashire.

Another interpretation might be to use the J code for the letter J (!), which could be a zero at the end of A-I == 1-9.

Like HW says, the numerical bit is not quite clear. Any more clues KT17?

Jerry