Lock trouble

I recently changed all the locks on my year 2000 TD5 Defender. All well for a few days but now the passenger door is locked and cannot be unlocked from outside or inside.

What's my best option for getting it open?

What is happening with the inside Lock button and door release ? Are they jammed up or do they feel loose ? By " lock's " do you mean just the barrels or the whole door latch unit was changed ?

Handles were replaced as well as locks. Inside lock button will pull up but doesn't unlock. Door release pulls out but doesn't do anything. I think one of the clips has pinged off and a rod fallen out inside the door. Considering undoing the hinges but there is a flange on the striker that I assume will stop it coming away from the post.

I had that and in my case the latch itself had failed.
I got mine open by sawing through the plastic spacer on the b post (and hence the screws) from inside using a sabre saw.
You can go all Rambo and force the door card off , which I did, but couldn't see anything amiss but you could work the latch manually if a rod has come off.
New plastic spacer and screws was cheap if it come to that.

I seem to have dodged a bullet. By holding the inner handle out slightly and flicking the locking button up and down I managed to get it to unlock.
Everything back to normal after that so I don't know what caused it. I will leave the door card off until I find the cause.