[clio '99] Battery drain problem

Hi there, I have chance to buy really well maintained clio 1.6 petrol auto with only 66k miles. There's one problem- battery goes flat overnight or maybe little longer. With engine off, I found ~500mAh drain on + wire going to fuse box in engine bay, nothing on other one + going in engine direction. Weird is when I removed fuse named "multi something", 5A it was, it gone down to ~40mAh on the same + wire, still nothing on other +. But then starter turns but engine won't start. As far I know there was also something wrong with alarm diode inside which caused indicators flashing with diode. I cut off this two wires from hazard warning light switch, so now it's fine, but something still drains the battery. I was told it started to happen since car came back from so-called-mechanic after some power steering job done.

Please help me find the problem. I don't have any clio electronic schematics.

Thanks in advance