I am trying to book a train or bus from one of the London terminals to Edinburgh on 2nd July.

I will be arriving at LHR by flight from Bangalore in Air India airline. I will have checked in luggage. Suppose my flight scheduled arrival at LHR is 1 PM and I book ticket from London by 3 PM and flight arrives late in LHR and I miss the train/bus, do I get some refund from airlines?

What is the procedure? How much can I get? Do I get it in the spot?