|Otherwise one thought would be that if you found some good condition used diapers in the US (or Canada) that you were comfortable with, the sender can mark the value as low (think it's something like $45 that goes without trouble) and label the box "used goods, not for resale" etc. I had to do with for my sis when sending her linens to the UK. Import tax wasn't a problem then, and if customs opened it and saw used diapers I doubt you'd get a tax bill! Obviously that's more hassle than ordering from a shop, but might work for you and save you a bundle of money (given the currency differences between the dollar and pound, anyway).
Another thought is to look into Popolinis. They are very similar to ME in styling (think there is actually some bad blood about that and copyright infringment disputes). They are made in the EU and could probably be sent to you pretty easily.