Thanks for your reply.
Standard Class Off-Peak Return tickets would cost you £126.00 on some services or £199.50 on others. Standard Class Anytime Return tickets cost a whopping £301.00.
East Coast Trains unusually offer a First Class Off-Peak ticket at £328.00. A First Class Anytime ticket costs £415.00 (which is somewhat less than the 50% premium normally added on for First Class travel).
However if you book now (before all the bargains have gone) you can buy a Standard Class Advance ticket for your outbound journey for £38.00 (or even less on some journeys) with the return journey typically costing £28.50 (or even less on the last two trains back). So a typical total cost for Standard Class return travel might be £66.50.
First Class Advance tickets for your outbound travel are available for £70.50, with First Class Advance tickets for the return journey priced at £50.00, making a total of £120.50 for the round trip.
So if you've made your mind to travel First Class, BOOK NOW and pay £120.50 per person, rather than paying at least £328.00 (and possibly £415.00) by leaving it until later. A SAVING OF OVER £200 PER PERSON IS DEFINITELY WORTH HAVING!!!
Check times and fares here:
http://www.nationalrail.co.uk/
(You can also book via that site. The link will take you to East Coast Train's booking system).