I wonder…probably only if

[charles]

 I wonder…probably only if they are small, young weeds. Unless the compost was thick and even enough to cover all weed leaves, some will re-grow, especially around the edges of beds. In your situation the polythene was a good idea. Or you could have put down some cardboard (after removing tape, staples etc) and covered that with the compost. Cardboard is liked by worms, is good soil food, allows rain through and  exists for long enough to kill most annual weeds. And unlike polythene it does not need removing.