On Mon, 15 Feb 2021 13:39:47 +0000, S wrote:

I have a bathroom UPVC window that has a worn bottom hinge and two
misted up DG glazing units.

How do I measure up the glazing units so that I can get replacement
glazing units?

How do I get the beading out of the frame in order to swap the glazing
units over?

How do I measure the hinges so that I can order the correct ones? I am
happy to replace the top hinge as well so its a matching pair.

In my experience, allbeit about 20 years ago, d glazed units are quite
cheap. Ask a local supplier, not a chain installer. They'll tell you
how to measure if you can't finfd the information using Google.
For the hinges Google for double glazing spares. You'll probably find
someone offer matching replacements.
Then you'll be able to make an assessment about the best way to go.