Hello Daniel Stott,

Simply you can enter to recovery mode by fallowing instuctions,

• Power off your device.
• Boot in recovery mode by pressing and holding Volume Up and Power Button at the same time.
• Release all buttons when the Sony Xperia Z3 Compact screen flickers and in a few seconds the Recovery screen will appear.
• factory reset your phone ( use volume keys to navigate)
• reboot phone

Now you are free to use your phone back

Note: All data will be lost