Competent service, outrageous mark-up, bad attitude to Ts and Cs.
Booking and getting tickets seems to have been competently done (on the day we'll find out if all's well there) but I should have researched the options better. Effectively, RailNinja is charging a 72% mark-up on the carrier's price. They are, I've found, an expensive agent anyway. But in part this mark-up is because they couldn't book a train/train option that they listed (I couldn't have booked it with the carrier either) offered me a train/bus alternative but still took payment at the train/train rate. When I queried this they said they "don't provide partial refunds in such cases". If there's a next time I'll go to the carrier. EDIT RN's reply below ignores the point. I am not "unhappy" with my choice. I am unhappy with being charged the train-and-train fare (£248 for two tickets) when you could only sell me the train-and-bus option which would be £236 for two tickets at the price advertised.