I have off peak tickets valid for this journey, with a family railcard, for 2 adults and 3 children. Please can someone give an idea when I will be able to reserve seats? Also, are there likely to be weekend first tickets available to book in advance for this train? I tried to reserve at the station a couple of weeks ago but they said reservations weren't released yet. I also might be looking to get weekend first and they said there may only be few advance weekend first available. So I'd need to be quick when they were. Thanks!
As in, you've already bought off peak tickets?
Just a couple of heads up:
If you have a through ticket Penzance - York it will be cheaper for you to refund this, potentially even paying £10 fee per ticket, and rebook with trainsplit.
There is normally no advantage to buying flexible tickets in advance, but on this occasion you may avoid a fares rise by doing so.
Weekend first will be available depending on how many seats are unreserved/unused upon commencement of the journey - I've seen the TM on Aberdeen - Penzance turn away prospective upgraders due to (almost) all 1st seats being taken already.
If you contact XC on Twitter they are normally fantastic at making seat reservations, but if you don't yet hold a 1st class ticket they won't reserve one for you, instead they will be happy to reserve you Standard seats.
You could also try the XC 10 minute reservation system to reserve 1st class seats by text on the day - full procedure on their website.