I'm sorry to be negative I purchased a memory foam mattress very very similar, the shrink-wrapped type. Sadly it never fully inflated. I think that with you not being allowed to take the inner plastic off, it is going to have a hell of a job 'inflating' properly, let alone you getting a good idea with a silly layer of plastic on it!
Also, if these are the ones that are only made for Ideal World............ wouldn't buy one for a tenner tbh