Help with Brake line fittings

I came across a XJ6 rear end in the scrap yard and rather than allow to waste away I put it into a kit car I was building. The Brakes are inboard near the pumpkin and the brake lines servicing the two calipers join up at a union and everytime I try to fit a new double flared (inverted)line , i get leaks. Is there a european bubble flare or Whitworth or??? or maybe an american to ??? fitting i need. Mick