On Monday, October 24, 2016 at 12:44:10 PM UTC+1, Michael Chare wrote:

Why remove the handles? I would try to drill through the Euro barrel at
the level of the retaining screw and then hope it pushes out.

Michael,
Yes, that seems to be an option - if I can figure out what level the retaining screw is.

Does the key keep turning from both sides of the door?

Yes. The inside has a flat knob rather than a key+keyhole, but yes, they both turn freely, with no effect, on each side.

These people are helpful and might know the best way to approach the
problem:

http://upvcspares4repairs.co.uk

Many thanks for the input. It looks like one option would be to take the pins out of the hinges and try removing the door. I might try this when I get back home, weather permitting.

JD