Recently back from Malta and my sons pouch containing insulin went through scanner together with the rest of his diabetic kit, also accompanied by a Drs letter. No problems heading there through Belfast then Gatwick, only on returning from Malta did the security lady run off with pouch ( suppose cause the little cartridges contain liquid!!) None of security bothered to look at Drs letter, and when told what the pouch/ bag of kit contained, we found they didn't take much interest, just popped it all through x-ray.
Hope this helps.
Suzi x