Watched a program on tv a few weeks ago. At UK airports almost all flights from the Canaries, (Spanish, but non EU) had the luggage x rayed on arrival at the UK. Customs then identified the suitcases deemed worthy of further investigation. Customs officials then stopped the people when they picked their suitcases off the carousel. So if you've never seen anyone stopped at customs on their way back from Tenerife, Lanzarote etc, then the chances are, they haven't risked it either.
PS me and the ex wife, used to do the tobacco run to Calais/ Belgium once a year (for our own personal use) One year we went to Calais and could hardly get any tobacco whatsoever. At the Calais ferry terminal though, about half a dozen people came in with large sacks of tobacco, opened the sacks and proceeded to flatten the 50g packs inside, by stamping on the packs. Anyway, they were hiding the tobacco in all manner of places, even had kids with them in pushchairs, so the kids were sat on hundreds of pounds worth of tobacco. Young kids with back packs too.
About half way across the channel, I asked one of the people if I could buy 30 packs of tobacco off them , to which the reply was "Nah mate, I can make a fortune selling this back ome for £3 a pack." I replied that I was willing to pay £2.50p a pack." But if he wasn't interested, then the best of luck getting off the boat at the other end. He followed me half way through the ferry before saying he'd sell me 50 packs for £2.60p a pack.

(bloody cheaper than we could buy it in France)