Can you post the model number please. Its usually etched into the door frame in the top left corner as you open the door and starts E-nr.
Also do you notice it getting hot during the wash?
Ok if the dishwasher is getting hot then thats fine.
As to the water pressure being reduced this wont effect the dishwasher in washing as once its filled with water it has its own spray motor which sprays the water around so it doesnt matter if the mains water pressure is reduced as that wont effect the water inside the dishwasher spraying around.
What you need to do on this is remove both spray arms inside the dishwasher and give them a good clean out. Make sure all the holes in the arm are clear as if they get blocked they can cause poor wash results in there.
But if the spray arms are fine but its not spraying at full pressure then its usually the wash motor that fails. As if these go weak then it struggles to spray the water around the system at full pressure and gives a fault like this.
But check the arms first as this s something you can do easy on these. But if they are fine and its still not washing as it should then its possibley the wash motor itself at fault here im afraid.
The motors on these are about £120 roughly.
But i will admit they are a complete nightmare to fit. As the base is a sealed unit so you normally need to remove the metal tank from the base which then turns this into a nightmare job.
But what you can try is a fixed fee repair from Currys Knowhow. They do a repair plan for about £120 all in. So for that price they will call out and fix it and thats all you pay.
So its roughly the same price but they will do it for you which will be a lot easyer.