We have recently had installed laminate wooden flooring by a professional company in our lounge but there are various areas in the lounge where the laminate floor dips, should this happen -as it is was installed on a concrete floor and as far as we are aware it was an even concrete floor. Additionally what could be causing the various dips?

The floor has probably always had dips but you could notice them before. The installer should have shimmed the floor when there was a dip. If he did not you job is worthless and will need to be redone to avoid the floor bouncing.