Todmorden has a railway station. There are plenty of mainline trains to Leeds or Manchester where you can change for Todmorden, which is approximately 50 minutes from Leeds. The trainline.com can help with identifying and booking trains from your starting point to Todmorden.
Buses are available from Victoria Coach Station, in central London to Todmorden. The journey from London to Todmorden takes approximately 7-8 hours.
These links provide information about various travel methods to Todmorden:
If you decide to fly, there are two airports near Todmorden:
Leeds-Bradford & Manchester. Leeds-Bradford is 30 miles from Todmorden and Manchester Airport is 36 miles.