On Tuesday, April 29, 2014 2:26:27 PM UTC+1, Mervington wrote:
I've been using lance type sprayers for many years. We have quite a

large garden (around an acre) and part is kept in a semi-wild state.

However, weedkilling is necessary (nettles and the like) and I am not

well enough to do that manually. I use a lance sprayer with a 'shroud'

on the nozzle.



My old one died recently, and I bought a Hozelock 5ltr. Unfortunately,

it has a major problem for weedkilling. The spray continues for 4 or

5 seconds after the trigger has been released, and the nozzle can still

be bleeding a minute after releasing the trigger. Hozelock replaced

the trigger, but with no improvement.



The trigger is certainly more comfortable to use than old types but has

this particular problem. Does anyone know of a lance type sprayer

where the cut off is just about instantaneous, please?
Mervington

Yes, but much more expensive than hozelock. A truly professional machine supplied with proper herbicide nozzles that give a more sharply defined spray pattern and will last for ever.
It's called Bastion - can't remember who makes them but Google or your local Agri merchant should be able to point you in the right direction. It's a 15l sprayer but I tend to mix 5 or 10 litres for my garden (smaller than yours)
I buy 'Clinic Ace' which is a bit cheaper than Roundup and is used at 100ml per 5 litres. Read the instructions carefully.
Cooper Pegler also make good sprayers - defacto 'industry standard' but see post above for a fatal design fault with them.

Rod