You are going to find a wide difference of opinion on this subject particularly between UK aquarists and US. If you are going to do a naturally planted tank the plants themselves assist in maintaining water quality, also a planted tank is not a suitable environment for large messy fish, another plus in the water quality issue. Hang on powerfilters where the media is a disposable element usually a spun type synthetic fiber with acitivated carbon, zeolite or both inside are the least expensive easiest to maintain. The next step up is a hang on canister which has a more powerful motor and larger media area, an excellent one here is the Magnum from marineland.com. The next step is a traditional canister filter, these typically are placed under the tank and you plumb to a from, they are more complicated to set up but they move large volumes of water and clean it efficiently.
Our brothers across the pond use mainly in tank filters in smaller setups and canisters for large setups, the simple powerfilter popular here in the US does not seem to be a favorite in the UK.
Hope this was some help, Good Luck, Scott
