vauxhall corsa - wont start possible problem with battery?

Hi I'm trying to jump start a vauxhall corsa I think the battery has gone flat.. when key is turned there is a clicking/clunking nosie but engine doesnt kick in.. Have tried to jump start using a ford KA.. no luck so far... The interior lights and radio on the car are still working.. This happened yesterday when the car was stationary nothing was left on to flattern battery. it has happend a couple of times in recent weeks but engine has always started itself after a few mins of trying.. no such luck this time.

any suggestions/help appreciated