It's not something you want to swallow or get in your eyes. As it's alkaline, you can neutralise it with something acidic such as diluted vinegar or lemon juice and then chip/scrub the remains away. Ideally you'll want to dismantle the item first so you can prevent the rest of the wiring and electronics from getting wet.
Duracell used to have a guarantee whereby they'd repair or replace anything that was damaged by a leaking battery. I don't know if they still do in the UK - they do in the US, for example. Might be worth giving them a call on 0800 716434.