petrol gauge showing half full when empty..

[pjw]

Ok im not a dunce, and initially i thought that someone had maybe had some different gauges on and not put the needle on properly. i intended to just fill it up and reposition the needle.

i just got the car, and the guy texted me after (cock that he is) and said that when the petrol gauge gets to half its empty. he also said this started when he got the petrol pump changed.

the needle sits normally at the bottom when the engine is off then shoots up to full, as far as i know theres only about £20 in it.

is the pump in the tank on these things? maybe its knocked something when its gone in. wheres the sender unit? im worried its not the simple needle move and that the sender unit is paggered.

anyone else had this?