Has anyone used one of these .........

I agree with Val. I've used it one time in the past. But it didn't kill any weeds.

 

Cheaper way is to use ordinary Roundup and a small sponge (with rubber gloves obvs) which you just dab onto the leaves.

 

I think you should get on your knees & get working!

I've tried it on ground elder but I've not had much luck, it works on thistles but you need to give it several dabs before you get a good result, if I see any for a couple of quid I will let you know

 

£4 at Wilko, Ramsgate a couple of day ago.