Hi! I understand that Citymapper has switched your default city from London to somewhere in the South West, and you want to change it back. Let's get that fixed for you.

To revert your Citymapper app's default city back to London on your Windows device, you can follow these steps:

1. Open the Citymapper app on your device.
2. Look at the top of the home screen where it shows the current city name—it should say something like "Citymapper [current city]."
3. Tap or click on that city name. This should open a list or a menu where you can choose a different city.
4. Scroll or search for "London" and select it as your city.
5. The app should now switch back to showing London-based transit options.

If the app is adjusting the location automatically based on your GPS or IP address, you can try disabling location permissions temporarily in Windows settings:

- Go to Settings > Privacy > Location.
- Find Citymapper in the list of apps and turn off location access for it.
- Then reopen Citymapper and manually select London as the city.

Let me know if you need more detailed guidance or if this doesn't solve the issue! If you want, I can also share a handy video tutorial link on changing the city in Citymapper.

Are you satisfied with the solution I provided?