Sardonicus

@Kev I thought it would be higher too.  100's are nice to play and I'll definitely keep at least one bass with them on.

If you re-string to a lighter gauge (re-tuning to original pitch) then the tension on the neck from the strings is reduced (generally for same / similar string construction).

This will reduce the neck relief. ie lower action.

But you may need to re-adjust to get same playability in terms of fret buzz etc. 

Sure, but neck relief shouldn't differ between guages, so if relief did change you would need to move the truss rod to bring it back.  The lesser string tension at the same action would cause fret buzz, so usually you end up needing higher action.