Oh how I wish I could share a pint with you sometime to compare notes. Alas being at the other end of the country it will likely never happen, however here's my take on jubilee clips.
The jubilee clips are prone to collapse the unsupported plastic t-piece, because they do not grip evenly and the plastic stub soon ends up egged with heat or even worse collapses with too much pressure applied. You would be better going back to the scrappy and also collecting some of that spring type of clips which give an even clamping force. There are a few spring clips fitted to a KV6 that will fit.
This is the reason folks end up cursing the original plastic t-piece and buy an alloy t-piece instead because during the life of the car the original swaged pips clips loose their tension and start to leak, the clips also cut into the easily cut turbo hoses leading to leaks. some folks cut a little bit off and fit them with a jubilee clip only to find them leaking again. If decent spring clips and a light touch are used you will not have an issue with the plastic t-piece.
Having spent the whole weekend on sons ZS180 doing the timing belts and finding all sorts of leaks. I found the dreaded jubilee clip bodger had been at it on plastic housings too and had collapsed the pipe.
Jubliee clips work well on older cars which are mainly fitted with metal stubs but if you use them on plastic you are asking for a problem if you cant control the tightness of the jubilee clip.
Some plastic stubs have metal inserts where the jubilee clip will work fine such as the intercooler hose on the turbo models. MG Rover in their wisdom unfortunately decided to omit inner metal sleeves from the plastic connection for one reason or another to the detriment of the vehicles life if some heavy handed person sets to the car.