You wont have any security when transferring from T5A to B&C terminals. You will have a GC lounge in T5B, however you wont have any lounge in T5C.
I actually prefer the T5B GC since its very quiet compare to the GC in T5A. However if your JED flight is in T5C, time your travel to the gate carefully since there is no lounge. I usually give myself 10 minutes before boarding commences to travel from T5A to T5C.