Renault Kangoo fuel gauge sender unit quirey

I have recently removed the fuel gauge sender unit from the tank, to inspect it after tracing a fault, should there be a gauze filter over the inlet at the base of the unit, as I am a little concerned that it has come adrift in the tank.

The unit is a large white plastic cylider with various springs and pipes, it appers to have a telescopic action, and a swill pot in the base, the inlet hole is tiny, and would be easily blocked so I was wandering if the lack of this mesh might be the route of my fueling problem as there is a lot of crap in the tank. (I found a dead sanil in the body of the sender unit) This had floted in over the top as the inlet hole at the base is too small for it the get in that way.

Any answers gretfully recived.