BA is offer a new "hand baggage only" fare, which will initially be trialled on five routes, of which LGW-JER is one. It's quite similar to the Flybe "Essentials" fare basis - a lower fare for flying without bags, rather than a simple surcharge (which probably amounts to the same thing, but it's all in the spin!)
In other news, five of the ex-BMI A319s will be moving to BA's LGW base, so no doubt we'll be seeing them in Jersey during the Summer.