Amazon.com customs charges, VAT on postage

[Sodslaw]

I normally accept the fact of customs charges, its just what happens when you import discs, but thought I would look into my £12.47 charge on my blu ray order which cost $23.98.
The £8 admin charge is a rip off, dhl and fed ex dont charge this much so why should the royal mail?
The £4.47 charge did not equate to 20% of $23.98 as the current exchange rate is £1-$1.58.
With the exchange rate at that level the $23.98 equates to £15.07, so for 7p over I have to pay an £8 admin fee.
When royal mail calculate your customs charge they INCLUDE the postage costs, so you are paying VAT on this too.
Im going to call them on Monday to get clarification on this but shipping should not be applicable to VAT.
I have contacted amazon.com about this as the way they label your shipments has a total figure which incorporates cost of discs and shipping which MAY be confusing for the Royal Mail