I am going from Cheshire to Anglesey next week, evening journey, a single ticket, joining DH and DD who will already been there with car and caravan.
I found that the direct fast train from our nearest mainline station was much cheaper than a slower train, with one change, probably because the latter involved 2 companies. Difference was half as much again as the direct train. Going on the fast train was a no brainier!
I then discovered that if I added on the journey from my local station, rather than buying a £3 ticket on train, it added about £14 on, again guessing because it is two train companies. I plan to pay that segment on the train!
From booking my ticket on Tuesday, the same 2nd class ticket now is a £1 cheaper - however I managed to book 1st class for £1.50 more than 2nd - that option has now disappeared!
I would say check out the cost of buying the tickets separately if you are going on more than 1 train operated by different companies.