The industrial action planned for 30th November doesn't affect the railways and rail companies can't be held responsible for changes to your travel plans which are affected by industrial action elsewhere.
So, if you've purchased 'Advance' tickets they remain non-refundable. Changes to the date and/or time of travel may be permitted but you'll have to pay the difference in fares if the current fare for your revised travel plans is higher than that which you paid (but you won't get a refund if the new fare is lower). You'll also have to pay an administration charge (which is likely to be £10 per ticket).
If you've purchased a normal 'Anytime' Day ticket, an Off-Peak ticket or an Off-Peak Day ticket you can only change the date of travel by applying for a refund (which incurs an administration fee) and then purchasing a new ticket.
If you've purchased an Anytime Return ticket you can use it for outbound travel on the date on the ticket or any of the following four days (with return travel within one calendar month of the date on the ticket). To travel on other dates you'd need to apply for a refund (involving an administration fee) and buy a new ticket.
Chris