I regularly travel to various African or Indian destinations from LHR with a Yaesu handheld transceiver in my hand baggage. I mainly use it abroad for listening to the BBC world service but as I hold an amateur radio licence I can use it to transmit on the 50, 144 and 432 MHz bands. It receives everything from 504 Khz to 999 MHz and with a simple software mod will transmit on airband, marine band etc. Security at LHR, or abroad, has never shown the slightest bit of interest in it. Toothpaste or my cigarette lighter is of far greater concern to them!
When on an aeroplane, I remove the battery pack so there's no chance of it being switched on accidentally.