Can someone find me the cheapest train fare return from London Waterloo to newcastle-anytime return?
An anytime return is going to be far more expensive than if you buy two single fares knowing when you are going to travel. Trains don’t leave from waterloo, they go from Kings Cross. If you have to start at Waterloo, get the tube Northbound to Kings Cross. The train company is National Express and you can buy tickets from their website. I would call them to find out what deals you can get as they often know more on the phone than online.