Thanks Chris.

a) Would I be able to see the spacers or would they now be hidden by
beading?

b) Would I be able to see the sealant on the inside or could it be
hidden also?

c) I have older (12 years) cottage windows with =8mm double glassed
units, which I am looking to gloss; they appear to have been sealed
with brown putty (or putty like substance) both inside and out. To get
a clean line between frame and window, I was thinking of the removing
glass and replace it after glossing the frames - could I use the
sealant on these. Is the clear sealant a relevantly new thing?