[awf]

Thanks for your help guys, I have tried the bolts already, loosened them off and tightened again, they are both pretty rusty, the bolts on the right side pipe are in good nick though, I might try changing them over.

Have taken bolts out, given them a good clean with a wire brush, put them back in again with a bit of a tighten, still a little leak of exhaust gases but less than it was and no backfiring!

Thanks for the link, I'll look at getting a couple of gaskets and a set of bolts...