I pulled up on the at p1 so assumed you cant drive however it is still there so i just checked for you and you cannot drive it
GWR have 2 services a day in Brighton heading towards great malvern/bristol temple meads, I'm 99.9% possive one departs around 5pm
I got on it to see if it would take me to Hove, but before the tunnel it tells you that you have left the playable area and ends.