Lowara Idrotuba water pump - very noisy when toilet flushed

[CHALIL]

Prior to moving in to a new build conversion ground floor flat I pointed out that a water pump positioned in a large cupboard/store room made a very loud noise when the toilet was flushed and then the tap at the wash basin quickly turned on.A plumber was sent to rectify it.Seemed OK then started again - plumber sent to rectify, blamed the water authority for low pressure.Seemed OK again.Am aware my neighbour in flat above had had a fairly constant similar problem as I can hear their pump.Now  almost  each time I flush the toilet - the pump kicks in - I count 34 'pumps' before the cistern has filled and the pump stops,tap at wash basin not even touched, just the cistern emptied.Am concerned.TIs it a water pressure issue?Thames Water say not - unless I buy a pressure and flow test kit and measure it.Any advice on somethinhg I might try myself, or do I need a plumber? Could it be the toilet cistern and something wrong in that?I know nothing about plumbing...as must be obvious.