I built one for extra warmth for the seeds in the greenhouse, looks the same, got it last year in a discount shop at the end of summer for six quid.
I spent time separating the bits before I started and had no problems at all putting it together. I started at the bottom and worked upwards. (much to his disgust, he was digging and I know he was watching waiting for me to ask for help).
If you are taking it back for a refund, make sure that they have run out of stock first or they might just give you a replacement.