Hi Mart and Peter, I'm wondering if I've been given the wrong gaskets (cylindrical fibre/wire wool type). The exhaust is as in the picture, but the downtubes have copper rings welded on 3/4 inch from the ends, which stop them going farther into the silencer pipes. Thanks for tips about cement and clamps - I only use one per pipe, but will get another set.
In any case, I bought a stainless steel system (without silencer) from a breaker for £75 which I will be using as soon as I get through the MOT. I will be posting a photo of the system soon, which has SRX600 stamped on it, in case anyone recognises it, and can advise me on a suitable silencer or end can (anyone know where I can get a Supertrapp?) Thanks again, Rob