"London Thameslink" stations

[CallySleeper]

I'm trying to buy a off-peak day return from London Terms to Luton Airport, and I get this warning:

"This ticket is only valid on services leaving London Thameslink"

What does this mean? Does it mean the six Thameslink stations?

The crux of my question is - given the ticket type, would I be permitted to start from West Hampstead?

 

[MikeWh]

I'm trying to buy a off-peak day return from London Terms to Luton Airport, and I get this warning:

"This ticket is only valid on services leaving London Thameslink"

What does this mean? Does it mean the six Thameslink stations?

The crux of my question is - given the ticket type, would I be permitted to start from West Hampstead?

London Thameslink is: London Bridge, Elephant & Castle, Blackfriars, City Thameslink, Farringdon and St Pancras International. As long as break of journey is permitted then starting short at West Hampstead is fine.