We have a 30 day trip planned from Ireland to Copenhagen in fall this year. We have Eurail passes for the UK to Copenhagen portion with plans for 5 rail travel days. The first day for rail will be Holyhead (after taking Ferry from Dublin) to London Euston. We will each have two bags with us and our passes are for 1st class. I was able to make seat reservations for the following 4 train travel days (2 via Rail Europe site and 2 on DB site). I have found no way on the Avanti West Coast site to make seat reservations only. In all my searching I stumbled across the GWR site and seem to have made 1st class seat reservations in coach K (quiet coach I believe) at no cost for the AWC train we are planning to take. All I have is a printed PDF confirmation, no QR code, from the GWR site - it doesn't show that its for AWC but has the correct departure and arrival times. Is this all I need to ensure we have the seats indicated on the GWR reservation? I am just surprised it was possible on GWR and not on AWC's site and that it didn't cost anything.
Any help making me feel confident about this (or offering a better way to accomplish this if there may be problems with the GWR seat reservations) would be much appreciated.