Dell,
Is it a fire/acoustic separating floor between occupancies, or just to deaden sound between floors in one ownership? [Sorry, always more questions!]
Proper lino from people like Nairn in Kirkaldy is lovely and joints can be neatly welded.
22mm WBP T+G ply to joists @ 400/450 ccs or 25mm WBP T+G ply to joists @ 600ccs. Office loadings may need closer centres. Need to glue every joint to prevent creak as you can't nail through resilient layer.
Used to use resilient layer of 25mm quilt compressing to 6mm for sound deadening between floors? You could just use 100mm quilt between joists or 15mm BG soundblok board to u/s.... or proper British Gypsum fire/acoustic system for full separating floor between ownerships?
Building Inspector would advise if refurbishment as you don't necessarily have to improve existing floor if it is remaining in same occupation as long as you don't make existing situation worse.
[Edit: didn't notice ref to office at start!]