Postage is postage as far as I'm concerned, and I don't use it as another income generation vehicle to rip off the customer, unlike many online retailers.
I have, however, now decided to send all items via the slightly more expensive Post Office signed for second class service. This still ensures a timely delivery, and also provides a greater reliability at a still reasonable price.
Shipping costs are calculated by total weight.
All international mail is sent by the Royal mail tracked service.