Problem solved - thread can be closed/deleted.

[Mr Badger]

An old UPVC door that has been trouble free until now, but has seen many years of use so it's quite possible the lock mechanism has worn. Upon turning the key to unlock the door something strange happened and rather than turn from (to use a clock face) the normal 12 o'clock to 4 o'clock, the key now moves between 10 o'clock and 6 o'clock. Worse, the key is stuck in the lock (presumably because it can't be returned to the vertical 12 o'clock position) and the door will not unlock. WD40 and lots of tapping and rattling have made no difference.

Had a go at snapping the lock with a pair of grips. Vigorously manipulating it this way allowed the key to move freely again and unlock the door!

 

[Rroff]

Similar thing here - maybe some useful advice https://www.reddit.com/r/DIY/comments/muzhhc/cant_remove_key_from_lock_when_door_is_locked/

A bit of a Hail Mary but if you have a hair dryer might be worth trying to gently warm the lock - might be just enough to do something.