Try some Boss white jointing compound on the tapered threads Mark, works very well, couple of quid from Plumb Centre.
And don't forget to put the fitting on the pipe before flaring the end, then again everybody does that once....
and don't over tighten them.
Also, when you are flaring a female end push a male first then you make it into a female end. If you get stuck then give me a shout. I've also got the trumpets when you need them.
Regards....Andy