The Japanese radio station I listen to is ラヂオきしわだ, which is a station based in Kishiwada-shi, Osaka-fu. You can listen to it on the internet directly in your media player, or through their website, or they even have their own Android app to listen on.
http://media.radiokishiwada.jp:8000/radikishi.mp3
http://www.radiokishiwada.jp
http://play.google.com/store/apps/details?id=jp.radiokishiwada.SimulRadio
However, the thing with Japanese radio is that it obviously runs on Japan timezone... I notice you're in the UK, same as me. Radio Kishiwada starts each day at 09:00 JST (00:00 our time) and stops at 00:00 JST (15:00 our time). So right now, in the evenings when you want to listen to something, it is not currently airing (it leaves "world music" playing when off air). And another thing is that English language songs are played fairly regularly, not just on this station and but most others... ^^;
There are many other Japanese radio stations available online though. Another Android app I use is "Japan Radio" (which is where I found ラヂオきしわだ originally). This app lists LOTS of Japanese stations by their region where they are located in Japan.
http://play.google.com/store/apps/details?id=com.littlehilllearning.jpradio
On desktops and other devices it is just as easy to find lots of Japanese stations. Can use various sites like tunein.com and just browse by "Japan" location, like this:
http://tunein.com/radio/Japan-r101255/March 15, 2016 at 5:04am