97 300tdi drivers door has been getting harder to unlock with key (key goes in but will not turn) but after pushing and pulling door eventually turns. Has worsened to the point that now will not turn at all and cannot get the inside door manual release lever to lift. Having to get in via passenger side. Any ideas/advice?

There's series of linkages and rods from both the key barrel and the actual latch, handle and door pin. It could be these that have become dislodged or likely jammed by the sounds of it. It's all pretty simple when you look at it, take off the door card and I'm sure all will become clear.

I'm no expert, but just fitted new locks, handles and central locking so familiar with the workings to a degree.

Somebody will say if I'm wrong

Or the lock barrel itself has worn, they are cheap and easy to replace though

However most of the troubleshooting would be made significantly easier if the door was open.....try lifting the lock from the inside while pulling the handle.....I had a similar sort of issue, I just opened the door, took card off and greased everything, and was fine. I suppose if it carried on things could start to bend, which is probably whats happened with you.