Hi Andy1374, welcome to the community!
If you can't remember your passcode then you can do one of the following:
Run a software repair on the handset (this will delete all user data)
or Log into my Xperia (if you have previously set it up) > Locate the device > Press Lock > Enter code > now a different unlock box should appear on your screen > enter the code.
To run a software repair:
Download PC Companion or Bridge for Mac.
Running the software repair on PC Companion:
1. Install and open PC Companion then select Support Zone.
2. Phone Software Update.
3. Start.
4. Repair Phone
5. Continue
6. Accept data removal
7. Next
8. Wait for prepare
9. Select Phone
10. Follow the connection steps
Running the software repair on Bridge for Mac:
1. Launch Bridge for MAC without the handset connected.
2. On the Main Window select "Xperia > Repair Xperia
Device".
3. Ensure the phone is charged and select "Ok" in the
following window.
4. Select Continue on the following page.
5. Wait until the initialising step is finished the
continue as below.
6 . Select your model of phone from the list that appears
7. Follow the connection steps that appear, ensuring that
you are holding the relevant button down before during and
after the connection phase until the update/repair begins.
