Just moved hose and the back garden which is aproxx 20M x 10M is heavily
overgrown and looks like it just hasn't been touched in years.

I intend to strim down, remove debris, apply weedkiller and then rotivate
HEAVILY before planting/lawning.

I'm gonna need plenty of STRONG weekiller - can anyone recommend a good
product and the cheapest place to buy it?

Many thanks in advance.