I've recently heard (not read), that it's not wise to use even very well rotted farmyard manure in greenhouse tomato beds.
Is there any truth in this and if so, what harm can it do? Thanks for your opinions.....
No, no truth whatsoever. I have used rotted manure for decades with my tomatoes (pig, steer, cow, chicken and horse) and never had any problems.
Now in a heated greenhouse you could forseably come into some problems with unrotted manure going anaerobic on you but, if you add some browns like shredded newspaper or even better, mulched leaves, you should have any troubles.
I agree as long as its well composted.
if it were still fresh I could see where it could get really hot in the greenhouse from the heat of the composting manure. but if it is already composted that shouldnt be a problem.