If I booked a seat reservation but couldn't sit in it due to overbooking, am I entitled to a refund?

When you reserve a seat you're covered by our Seat Guarantee. That means if you have a reserved seat and you can't sit in it due to overbooking and our Train Manager can't find you an alternative seat, you can claim a refund for part or all of your ticket. https://www.lner.co.uk/customer-service/seat-guarantee/