wow - you'll need to be quick and very lucky, but this has just gone on freecycle:

OFFERED: 8' x 6' Aluminium greenhouse with glass (about 5 panes broken
at the moment, more may break during dismantling). Sliding door and
roof opening. Taker to dismantle and remove - plenty of free
refreshments also offered during this process!

hi, my husband would be very interested in this. we are going on hol on Wed for 2 weeks so wouldn't be able to pick up till after, would that suit you?

You'll need to register on Freecycle and email the person offering the greenhouse to be in with a chance of getting it.