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?

Is it internally or externally beaded?

Mark the bars for top/left/bottom/right and make a note which ones go
"on top" of which others, so you put them back correctly, use a blunt,
wide filling knife, to prise them out, but be careful not to damage them

Measure the actual sealed units, order new ones from local manufacturer,
also take note of where the packers are between the frame and the sealed
unit.

Get a non-marking rubber hammer to knock them back in with, after.

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.

Look for manufacturer/model name on existing hinges, see wha you can
find on the glazing repair websites, if the screws are loose you can get
'uPvC repair screws' with a more aggressive pitch.