Assembling a greenhouse on a community allotment (part one)

On a cold damp Friday morning in March 2013 the Good Neighbours gardening group in Chorlton, Manchester started  to assemble the newly purchased B&Q 10'x8' greenhouse with toughened glass (£904 inc. delivery).
John, our resident DIY supremo had already made a wooden template for the base, so today was about levelling the ground, digging a trench, ramming the earth flat, putting coarse grit and sand down and then laying & mortaring the breeze blocks. Finally the aluminium base was assembled and put on top of the breeze blocks. The following day we started to assemble the aluminium framed (see