andy wrote:
I'm fitting a new allimim/UPVC back door which is the size of
existing internal door frame but I have to remove the metal upstand
strip in the existing wooden cill ..... not sure what the correct name
is for this
I can't see how this is fixed into cill or the depth etc. and could do
with some advice how to remove it to make way for new door frame.

Grab it and pull it out. It will take quite some pulling, and
probably a bit of wiggling.