Train tickets

Also which is the best booking company. Lots of choices!

If you enter London > Hull in Google Maps Directions, select public transport, then you are offered four choices (and based on an arbitrary date and time):

• East Midlands Trains > Transpennine Express > Northern
• Virgin East Coast > Transpennine Express
• Virgin East Coast > Northern
• First Hull Trains

And then I would check the famous site - The Man in Seat 61 - and see what he would do.

Use the East Coast website for London Hull as they include First Hull trains details and prices but only First Hull run direct - about 6 times per day -, otherwise it is change at Doncaster at least once or twice per hour. Transpennine do the other 2 journeys. However you should be able to email the printable ticket.

When buying on line you are given a reference number which you enter into a machine at the station which then issues the tickets BUT to confirm identity you must insert the credit card used when collecting tickets. So book with a card he will be carrying whilst travelling. You must also specify from which station you intend to collect (the booking will default to the first departure station unless you specify another station).

You can book any train, on any UK rail website (or by phone +44 (0)845 7 48 49 50*), regardless of what trains or routes do the specified trip.
Avoid 'The Trainline', as it often has additional fees that other retailers don't.
An advance ticket will generally save a lot of money over buying 1 on the day. There are strict conditions on an advance ticket purchase though. The traveller must board a specific train on a specific day or the ticket will be void, no refund & in addition another (more expensive) one will have to be bought. The only time that rule doesn't come into effect, is if the traveller misses a train through a delayed or cancelled connection.
An 'E-ticket' is 1 you purchase online & print off for travel. However, the traveller is often asked to show the card it was booked & paid for with, so if you're buying it for him, that could pose a problem, unless he can have your card while travelling, or you book/pay for the tickets with the card he's travelling with. The same applies to collecting from a 'Fast Ticket Collection' point. The card has to be inserted into the machine before a ref./collection number is keyed in to collect the ticket/s. His best option is to buy his ticket/s in advance, once in the UK, a few days before he travels.
Re: Man in Seat 61, as suggested above has some good tips, but its website's timetables are sometimes a bit out if date. However, getting from Hull to Edinburgh - via Manchester, is a series of very easy connections & the trains are frequent. I've done both routes many times & the journeys are very pleasant.
Northern Rail often has local, slightly cheaper promotions which may include your son's chosen routes, however you need to sign up to its website's e-newsletter to get them 1st hand.

*National Rail Helpline - times, fares, tickets & options of how to buy & collect are all available on that number. There could be a different number to call from outside the UK, have a look on its website.
Good luck with everything.
Quick edit to Throstle's post above:
The reference number is different to the 'Ticket Collection Reference' & will not work in the collection machine.

#3 has the shortest way of how he does it.

why are you doing it? He'll need the card anyway, so best he does it.

remember that many of these tickets are non-refundable and some specify exactly which train to get. Miss it and the ticket is not valid.

As above, to collect at the machine you need the card that was used to book. however, you should be able to get the tickets sent to an address in England. Any contacts you could sent the tix too?

I've pre booked, printed out my ticket and used this on East coast and Transpennine without ever being asked for my credit card. Iknow the credit card used for the booking is needed if collecting from a machine ( and even with self printed tickets on Deutsche Bahn) but never known a card required with a self printed ticket in UK

It's right what you say, not every time will you get asked show your card, but it 'Does' occur.

Thank you all so much, you have answered all my questions. He has the credit card with him, I hope, so we'll do the ticket machine option. I really appreciate all the information and help. Thank you.