Edinburgh to London - August 7th. London to Edinburgh - August 12th ?

I have two single tickets from Edinburgh to London on August 7th and two single tickets returning to Edinburgh on August 12th. All tickets require a young person’s 16-25 card. The tickets originally cost 90 (see details below). The asking price for all tickets is 70. I will happily sell them individually either. 2 Outward tickets - Tuesday 7th August 2012 – Dept. at 17:00 (19.30 each) 2 Return tickets - Sunday 12th August 2012 – Dept. at 12:00 (25.75 each)