What's the best way to effectively kill weeds and unwanted grass seeds?

I removed practically 500kg of weeds from my garden this last two weeks. I
filled up my two sun exposed post pillarbox-type compost bins to the brime
with weeds and cut grass. I then threw the rest away in my two huge council
compost garbage bins.

The compost bins are exposed to the hot westerly sunshine. I plan to hold
the bins there til next Winter then use them- ie a period of five months.

I also have an open compost cage where I throw my lawn clippings and leaves.
But because its in an exposed and hot area- the compost thens to dry up. I
turn it over every now and then- it helps but...

But I'm worried that when I use them for top dressing and for my flower beds
next year, the weed and ex-grass seeds will germinate and give me hell.



I heard that placing the pulled out weeds in a plastic container filled with
water- will cause it to rot and kill the seeds.

Any ideas?

Cheers
Wilde