Unfortunately, inexpensive soundbars can sound just as bad as the TV's own speakers. To get a worthwhile improvement in sound quality, you'll need to spend over £100...the Samsung HW-J355 is the cheapest one with decent sound. (From December's Which? test)
Have purchased and opened the box for the instructions to install the sound bar as recommended by Which, gingerjbee...am a bit anxious now. As I am reading it it needs a Samsung TV, that mine is not.
Am getting someone else to install it so we shall see.