Ok, bit of history, used to have an opening to a conservatory which
was removed, space bricked up and window installed. 2 problems builder
didn't have correct soldier bricks at time of job so a 2 course gap
was left between sill and new wall. Soldier bricks inserted at a later
date so I am guessing the mortar that I can see between top of soldier
bricks and window would have stuck to the sill. Second problem,
glazing of window was done incorrectly (not cross braced) causes the
sashes to become out-of-square (jeld-wen inspection pointed this out).
Hence,I am replacing window and doing the job myself :-).