This Anglo/Jap "joint project" thing is played up too much. The car was designed by Honda 100% and on sale in Japan as a Civic a year before it was introduced by Rover. I understand from a very old friend who is quite well in with Rover, the Roverisation process meant little more than recalibrating the suspension, fitting the (quite brilliant) K series engine, working out where to put the plastic wooden door inserts and the choice of velour on the seats. When it was first introduced, it was a thoroughly wretched vehicle. I know, I had one as a company car. Not a patch on the previous two Rover 200's I had.
Stevens redesigned the body kit post BMW and as you say the suspension was tweaked, transforming the vehicle. But I think your car is a diesel, which, (and I stand to be corrected) has a Peugeot engine. The gearbox in the 400/ZS is also built under licence by/from Peugeot.
I understand Honda gave up the design as it is no good to them any more. There have been two generations of Civic since the 400 came on the scene. IMO, the Civic Type R is the epitome of a modern hot hatch. That the ZS is now so good to drive is a testament to the age old British skill of making a silk purse out of a sow's ear.
Robbo, I'm not knocking your choice of car, it has much to commend it, but I can't see that an old Japanese chassis/body, with all major components designed in Japan, a froggy drive train and a mirriad of other more minor components made abroad qualifies it as 100% British.
Just my opinion.
