old heating manifold

hi can any one help, I am fitting a new rad in my kitchen and ever thing was going well till I went to connect the new 8mm micro bore pipes to the existing manifold.it appears to be an old imperial manifold but it is already supplying the rest of my rads through 8 mm pipe. the problem I am having is when I removed the 2 nuts with block off.s to fit the new pipes the nuts will not compress the olives and a new 8 mm nut from a compression joint will not fit on as the threads appear different i did think about using a 8 mm compression joint to make the olive a tight fit then cut the pipe to remove the 8mm nut and fit the old imperial nut then re join the pipes ,this seemed a bit of a pain so I just refitted the stops for now till I can get some advice about the best way to solve this. can any one tell me if this would of worked as all the other pipes have the old type nuts on but with olives that have compressed

 

I am already using 8mm micro bore but the nut off the manifold does not compress the olive onto the 8 mm pipe.do you mean use a tee on another pipe before the manifold because I always thought this is bad practise as I could of just teed into a near by rad to feed my new one

 

well that advice is as much use as a chocolate tea pot, spend hundreds on a new system ? is that what you would advice a customer is it