Thanks Guys for the various replies .....

From this site and one other it looks like the consensus opinion is to give watering edible plants with this water a miss ….

However I am still making use of the water as the down pipe from the shed now runs away under the greenhouse to keep the floor moist in summer …… Nothing is growing in the soil and shingle under the greenhouse, but hopefully it will keep the moisture levels up a bit in mid summer.

Cheers all .................