There is a travel agency in the Netherlands who specialize in train travel, de Treinreiswinkel, and who will get you UK train tickets, as far as I know also at the special low cost early booking fees.
You do pay for the service, so you do need enough of a win on the cost of the tickets to make it work.
Your Dutch bank card is likely enough to get tickets out of the machines in the UK, most are, check with your bank whether yours is restricted to only Dutch use, (unlikely but possible) but non of the bank cards (debit cards) can be used for online or foreign buys.
If you buy your tickets using someone elses credit card, you should have that particular card with you when you collect the tickets. If possible, have the tickets send to your house.
When stuck, try any card with a magnet strip even a library card can do if it has a strip.
Or go to the ticket window and ask for the ticket there, explaining that you do not have the card on hand, (tell the truth if asked but you may leave it vague if not asked,) and give them the print out of the ticket confirmation.