Imoseley

I have a problem regarding the Jenna Coleman photoshoots on the Saturday which I have a ticket for, basically I'm coming from Gloucester, quite a way away from London and on the train but It probably won't arrive until half ten at the earliest. This means I am in with a chance of missing the first photoshoot times and as I have train tickets booked to leave at five I am going to miss the second slot too.... I'm really worried and dont know what to do.. Is there any way of getting straight in? Unfortunately only have standard tickets and my photo ticket number is #479, please help?