In line with Royal Mail price increases, my P&P costs within the UK are now as follows:
£4.30 (normal first class)
£5.30 (Signed For post)
£9.00 (Special Delivery)
For international orders, I now send all orders using a Signed and/or Tracked service, and the shipping costs for these are:
Europe - £10.50
USA (up to 100g) - £13.50 *
USA (over 100g) - £15.50 *
Canada - £11.80
Australia & NZ - £12.30
I do combine orders for a small additional cost (usually no more than £1), and I usually have a discount code you can use in my online shop to avoid further shipping to be charged where you've already paid it on a previous order - contact me for more information.
* UPDATE As from 1 July 2020, Royal Mail are increasing their prices for shipping to the United States by up to 24% (depending on the parcel weight and shipping service). This is in response to the USPS increasing its fees paid by Royal Mail. Pricings for the rest of the world will remain unchanged, but shipping costs to the United States will be increased to £14.50 for International Tracked & Signed post (the best shipping method I've found), which is still competive when compared to other courier companies.