If you would like to pledge multiple tiers just increase your pledge by the appropriate amount - we will send out surveys for details when the project funds!
International shipping is a flat rate of £10 for all tiers. Kickstarter will add this when you pledge.
Yes you can, up to 2 sets per pack can be exchanged for something of equal (or less, of course) value. If you want to exchange for something of a higher value just add the difference to your pledge.
For example from the Complete Set you could swap a set of Security Walls (£12) for a Vehicle Workshop (£14) by adding £2.
Don't see the answer to your question? Ask the project creator directly.