These are now available SIM-free through Sony’s own site for £549 (full version), with the Compact incarnation shipping for £429. However, the same phones are available on pre-order from Amazon too, with a shipping date of September 29 given. Interestingly, the Xperia Z3 comes in at £529 on Amazon, a whole £20 cheaper than Sony itself.
On contract, Vodafone is also now offering both handsets, starting from £30.50/month and £38.50/month for the Z3 Compact and Z3 respectively. And if you can’t wait for shipping, you can also go in-store to pick one up.