Cheers guys.
I don't have the bass in my possession yet to look it over again and take any measurements but I'll be very cautious if I do attempt anything, especially since it's not mine.
I suggested putting bass into a luthier so maybe he will find out a cost for that. He's a keyboard player who likes to dabble on bass so I think he assimes it isn't complicated to sort action issues etc.
Maybe a luthier will know if regular steel flats can be put on. The guy doesn't like the bronze roundwounds.