Sorry for delay in replying but sunshine has kept me busy
Garage did replace with cup variety although have not checked whether they did the exhaust valves as well.
Egr valve is still blanked off and have tried tying back the butterfly valve as I know this is done on some ice cream vans at shows to cut down on smoke but this has had no effect on the blue smoke.
Reckon its got to be one of three things
1 The head
2 Oil seeping from oil channel to cylinder through leaking gasket
3 Oil ring
Since she puffs blue on start up after having a long run the evening before to get home and presuming that oil does not defy the laws of gravity and seep upwards past the ring overnight I think I will replace the head with another one I bought as a spare and see if this gets rid of the problem. Thanks for the suggestions Warbling toad