I spent a couple of hours last week trying to dig up some of the
nettles at the edge of the "grassed" area to see if it was possible to
remove them without sacrificing what little grass remains. However, I
discovered that there is a web of inch thick nettle roots about 20cm
below the soil surface, and that if I tried pulling them up, the
result looks like the surface of the moon. Am I right in concluding
it's better to redo the lawn from scratch?

I seriously doubt it. I'd try and start with a clean slate if I were you.
Stingers can be got rid of eventually if you keep cutting/pulling them, but
the roots just sprout again. I think it's likely to take a couple of years
to control nettles like that. Eventually they should die. But with such a
well established patch I think it really would be easiest and more
effective in the long run to get rid of them first. Either a weed killer
(maybe?) or "simply" the hard way by pullign/digging the roots up as much
as you can. At the same time you can get rid of the other weeds.


I consulted with our landlord, who is willing to run his rotorvator
(what is this?) over our "grassed" area, which he says will let us
seed the lawn again. However, I'm dubious as to whether this will get
rid of the nettles or just distribute their roots more widely round
the garden and let them take over even more space.


Once you've got the most of the roots out, a good going over with the
rotavator would be a good thing.

Tim