I'm thinking now, rather than go to all this palaver, just to re-sell the thing straight back on Ebay without even opening it, what do you think?
You will have wasted £18 shipping plus eBay fees even if you do get £32 for the item.
I'm sure it will be just fine if you take steps to weigh it down. Four or more 6 pint milk flasks full of sand tied to that lower side rail will take a heckuva wind to shift them.
I wouldn't bet on that, WG. I was convinced that mine would withstand a hurricane after it was lashed down, but once the wind gets in, and it will, it's bye-bye tunnel.
If it's relisted at the same buy-it-now price, with the same postage cost, then I suppose you will only end up losing the price of the Ebay fees.
Believe me, if you plant it without taking adequate precautions, then you will never stop worrying about it. Far better to cut your losses and buy a second-hand greenhouse out of the paper. Even though you don't have transport, the previous owner may deliver it for a bit of extra cash.
I've seen 8x6 ally greenhouses in the local Ad-mag, dismantled and ready to go for £50-60. Add an extra tenner for delivery, and you're laughing.