Personally I think putting a slippy dif on a small hatch like the Clio goes against the "old school" thrashy hot hatch thing that the Trophy does so well. That said there are a number of threads on ClioSport where folks have fit the to 172/182s.
IMO every front driver is transformed by LSD, even the helical type as per Quaiffe, and even for road use.
On the other hand, the trophy is quite well resolved to work without one, and it is not cost effective to fit one. I have been quoted cca 1200 pounds for the fitting alone. The gearbox has to come out I have been told.
OTOH if I ever need my gearbox reconditioned (or replaced) then it will definitely be going back with a LSD. Possibly the Gripper clutch type, if someone does not start to produce a cheaper one.
I agree with 480bhp, for track work LSD will transform the trophy.
I'm thinking of getting an LSD fitted to the T next year (hopefully). I think it would benefit significantly to be honest (although I'm not measuring significance in terms of tenths of seconds off lap times). I dare say it would be a waste of time and money if the car doesn't see much track/B-road 'spirited' action though.
LSD can totally make a car, especially a FWD car. Our FTO has a Torsen LSD (like Quaife) and it totally makes the car, you can get the power down so early out of bends, and on track at Silverstone it was brilliant. Another good side effect was the car was excellent in last years snow as you could feel the diff really working hard to get best traction, you would never have believed it was FWD car the way it easily dealt with the lower levels of grip, our neighbours RWD Auto Merc never moved in nearly a week.
There is a reason why the Honda Integra Type R DC2 is so highly revered and a lot of it are down to its Torsen LSD.
The Championship Edition Civic Type R with Torsen LSD is so much better than the standard Civic Type R, 3 secs around Bedford Autodrome better, and on road really made a difference when I test drove them.
We have fitted a Quaife LSD to our Cinquecento track day car and it only has 120bhp.
Plate diff diffs as used to be fitted to Mini's can be very snatchy, but Gripper Diffs seem to have made them much more usable on road cars. But in general they are the best for drag strips.
Viscous diffs, as fitted to Fiat Coupe Turbo's and Subaru Impreza's are a bit lazy and really need a big difference in wheel speed before working.
Having done about 30laps of Castle Combe in a friends Clio 172, a LSD would transform it, being able to get power down sooner and not wasting it away by spinning up the inside wheel.
Fitting a diff is not as difficult as you think if you have reasonable spanner skills and often can be done without removing the gearbox, dependent on access. Alfa Romeo sell what they call there Q2 diff, again Torsen, and again makes a massive difference to there cars, from the 1.9JTD's but really work well on the 3.2 V6's and Alfa sell it at less than £300, most folk only charge £450 to supply and fit as can be done without removing gearbox, should really have been done as standard on the V6 147/156 GTA's though may have not got reputation as an animal. I don't know Clio's yet, so can't comment on access.
As an aside, the Ford Revo-knuckle suspension is similar to what Renault used on hot Megane and I think Clio 197/200, but then if you go back to 1994 Toyota fitted to all GT4 ST205s to production end in 1999 and JDM FWD Celica ST202 and later ZZ model there "SuperStrut" suspension which does same thing, Macpherson strut front suspension but strut is fixed in place and steering is done with other components meaning less camber change of wheels as they turn, sure many of you have read how it works.