Sussed.
Various issues, the first is the flow sensors I have say they are hall effect o/p, I think either they are reed switch or open drain o/p, as they do not pull high, 1k pullups did the trick, it appears pullups are not provided within the esp on some of the gpio.
That made the thing work, but it would not boot while the sensors were connected, turns out if you connect to any pins except the I2C port it can mess up the boot cycle.
So I connected the sensors to the I2C port pins, fortunately for this job the port isnt needed.
All appears to work now.