You don't say what battery you want to charge.
Most battery chargers (I'm fairly certain the Pentax D-LI50 battery charger for the K10d and K20d, for instance) can handle the different voltage in the UK, so you only need an adapter (not a converter) like this:
AC POWER Travel Adapter Plug UK ENGLAND Type G BS 1363 - eBay (item 190285657909 end time Mar-10-09 20:02:56 PDT)
Just check the label on anything you want to plug in. If it says INPUT: 100-240v or something like that, it'll be fine. The same goes for the transformer on your netbook computer.
A hair dryer is a different story. Almost certainly it cannot handle UK voltage, so you will need a transformer rather than a simple adapter, but they are typically not able to provide enough wattage for a hair dryer! Leave it at home, use one in the hotel, buy one, borrow one, or dry your hair with a towel.