Have decided to treat both DSs' eternally sniffy noses and sneezing as dust mite allergies (the GP won't test..) so we're going to cover their bedding. You can get mattress covers on eBay for about 5 quid- are they any good? Or does one have to look at the 25 quid ones? And do they have to encase the whole mattress or is a slip over one ok?