Thanks for your advice Ron, it could be that do to my inexperience I had the bleeder valve too far out (I haven't worked on brakes since I was a teenager - a long time ago).
I don't have the reducer valve to the rear, mine is the single circuit, no vacuum assist system. I was using the old fashioned two person bleeding system. The fist time I tried bleeding, I used one of those vacuum units that you attach to the bleeder, without success.
Those special bleeder valves intrigue me though. There are other brands, I have discovered, most are called speed bleeders. I think I will give them a try, my old valves don't look too good and the caps are missing.
Tom