Announcement from Showmasters:

Unfortunately due to a change in his shooting schedule Thomas Dekker will not now be able to join us at Collectormania Milton Keynes, however we have been able to move his appearance to London Film and Comic Con in July.

We will begin refunding orders for the joint photoshoots with Chris Zylka and Lena Headey. This will be done automatically so you don’t need to do anything.
Tickets for the individual photoshoot will still be valid at LFCC, and you don’t need a replacement ticket at the event. If you are not attending LFCC and want a refund you can either post your unwanted Thomas Dekker ticket back to us or bring it along to CMK to be refunded (the original tickets will be needed, not just order confirmations).

**Updated with more info on London Film and Comic Con:

source (please note that Thomas has not confirmed this yet)

Due to a scheduling change Thomas Dekker is now attending LFCC instead of Collectormania Milton Keynes.

More info on the event can be found here.