It's all included, go on thier website...
https://www.buytickets.virgintrains.co.uk/categorymatrix.aspx
Or if that link don't work just go to virgintrains.co.uk and use the search function.
If you leave Brighton at 08:03 on the 17th and leave Birmingham the following day at 17:10 you can get singles for those journeys for £8 each on Virgin website.