ok took an axe to the oven to day
well almost
decided to move the bottom heaters up to the top
of itself it didn't make much difference
big bonus is I can now put what they call the crumb tray on the top shelf
effectively cutting the heated volume to around a third
by fiddling with the PID parameters I now get this curve
(thanks to retrolefty for a steer there!)
so I'll probably stop playing now and get on with the day job
(apart from adding a fan in the bottom, which now stays at room temperature

)