Most of these trains are one and done things straight from the departure station to London? The only experience I have was taking them in the other direction t

Most of these trains are one and done things straight from the departure station to London? The only experience I have was taking them in the other direction though, because I opted for a flight instead of dealing with it again to go back to London. Was a new experience booking a train ticket and seeing a quote of £250. I thought the machine was broken.