Now that we can't get Sodium Chlorate what's the best (as in
reasonably cheap + effective) alternative?

I recently used up my last bit of Sodium Chlorate on one part of our
large area of gravel and Pathclear on another area. The Pathclear
seems to have been totally ineffective whereas the Sodium Chlorate
worked well. So I'm not very impressed with Pathclear for a start.

I *want* the weedkiller to stay in the ground for as long as possible
so products that leave 'no residue' are most definitely not what I
want.

It's a big (like getting on for 1000 square metres) area of gravel so
price is quite a major consideration.

--
Chris Green