Thanks all for the replies. As luck would have it, I met a glazer last
night and asked him about this. He laughed and said he is constantly
"on call" to a furniture shop to do just this. He says it is easy peesy
- I just need two "suckers" (tile lifters to me) ; from the front prize
out the angled ehatever-he-called-thems, have someone on the inside tap
the pane twoards the front. He did mention to carefully rest it on a
couple of blocks; shoot in the sofa and reverse the procedure. I'll
gather the troops for Thursday evening (golf on Wednesday) and give it
a go...