How much work you looking at? Where are you located? I know a great guy in Cheshire (used to work at Bentley so has amazing credentials) but its not cheap.
You can do lots of things yourself very cheaply with a little time and elbow grease:
Wrap the interior aluminium with fabric vinyl for instance to give a more modern soft touch
The M sport steering wheel often looks like this, grab some alcohol cleaner and wipe it away and the wheel plastics look completely refreshed. Likewise, get a good leather cleaner and clean up the leather wheel itself and it looks fresh again
You can refresh the seats with some leather paint, just clean the seats and apply a few coats and it goes from this
...to this
Im very detail conscious and even did small touches like this, the plastic under the handbrake gets scratched up so I got a sample sized bit of leather look vinyl and wrapped the plastic section under the handbrake
Obviously if you want to go the whole hog rip everything out and get it new you can, but you will be looking at potentially four figures to get seats and door inserts done. Thats not including removing them all yourself, delivering them, collecting etc.