R writes
Given that there is (reportedly) a shortage of allotments around the UK
generally, and that with the overall demise of garden space urbanwise what
say the group about the idea of division of a very large ex-commercial
greenhouse into "units" for people to use ?

I think that's a great idea. Presumably you'd charge people for use?
Have you checked on allotment rents? - they're not very high - you might
find that people would not be willing to pay a rent that was economic
for you. Bear in mind that even if you decided not to heat the
greenhouse, you'd still need to maintain it, so your costs would be
higher than if you were the owner of a conventional allotment site.

You will need to provide a water supply.
What would you do about staging? You could leave that to the
plot-holders.

Thus far my idea is divide the existing 200ft x 80ft greenhouse into 10ft
square "plots", dividing if required by walls of tarpaulin or somesuch

I don't see the need for that, and it would cut down light especially
for the inside plots. You'll need to leave reasonably generous paths
between the plots.

with
the front of the greenhouse as a shop/sales area for produce etc (Already
exists in reality).

I'd expect most people would be more interested in growing for
themselves.

Would there be problems with cross pollination and other issues?

Only if people were saving seed for next year, and not much more than on
an allotment.

There would be a problem with pests - they can multiply and spread
quickly under glass.

There are decisions to be made about management. For example, are pests
to be managed using biological controls - a very attractive option
nowadays since so many of greenhouse pests are now resistant to the
pesticides available to the home gardener? Or are you using pesticides?
- you can't mix the two, because the pesticide will kill the biological
controls as well as the pest.

What temperature will you try to maintain in the greenhouse - eg what
level of shading in the summer? How much ventilation?
--
Kay