As apparently no one knew, I figured it out myself and have completed the task - these notes are for anyone else replacing a front seat belt and want to know what is involved for DIY, fortunately the pretensioner is not located in the intertia reel.
The car a 182 but probably much the same for all MkII Clio, I did the drivers side, it's the same for the passenger side except the bonnet catch lever needs removing.
Tools needed: 17mm socket, Torx star bits 20 & 40, thread lock, WD-40, patience and/or swear words.
Remove rear seat squabs; tilt forward 45 deg. and pull up/out.
In the boot, remove two 17mm bolts from either end of the cross member at base of back seats - these bolts go into the floor pan and will probably be rusted on the ends, work them out a bit at a time then some WD40, work them back in and out - better than stripping the threads or shearing the bolts.
Remove the cross member.
Remove the Torx 40 bolt in the bracket through to the floor pan at junction of the 1/3-2/3 back seat split, comments same as above, when this has been removed the bracket swivels back and the seat backs can be removed in tandem.
Remove the front seat base side cover, one Torx 20 screw at rear of the cover; the cover then pushes forward - you need to remove this to get the door sill cover off/on.
Partly remove the door seal and unclip the door sill cover - can be done with finger tips.
Remove the bottom belt anchor bar 17mm bolt and manouver the anchor bar out from the trim.
Remove the bottom rear seat belt anchor 17mm bolt.
Remove the front top seat belt anchor 17mm bolt.
Unclip the rear side trim panel, you should be able to do this by prising with finger tips.
Remove the bottom inertia reel 17mm bolt.
The seat belt and reel can now be removed.
Fitting is in the reverse order - with the following comments:
Give everything a good sweep out and any money found to charity.
Clean up the rusty threads of the floor bolts and give 'em a coat of copper grease if you have it.
Use thread lock on all the seat belt 17mm bolts - I used Loctite 243, tighten firm but don't over-tighten, it is important that these bolts are not over stressed, if you have a torque wrench - torque to 21 nm.
The door cill cover is a b**ch to get back onto the clips along side the front seat frame, there is just no room to manouver it - there may be a knack but I never learned it, watch you don't damage the (rear washer?) plastic pipe which shares the clips.
Take care when poking around near the seat base as the side impact sensor is just fastened there, a very unlikey event - but detonating that air bag would probably take you head right off when you're kneeling down there!
As with any repair, make at least a mental note, of how things have come apart and what bolts and clips go where, camera phones are a great asset.
Disclaimer: I take no responsibilty for anyone stupid enough to follow these instructions!