You shouldn't need any silicone for the connection Jiggy - I think that's possibly the problem.
The trap (plastic U bend bit) has a black "O" ring seal captured inside it.
This just screws hand tight onto the waste (metal threaded bit).
It's a kind of friction thing to make it seal.
If you use silicone, the ring slips all over the place and usually out of position - causing the leak.
We've all done it at some time or other :o))))
Can someone hold the basin while you take the pedestal out for access?