Genie wrote:
I have recently taken up tenancy in a semi-detatched victorian
labourer's cottage on the entrance track to a farm. The 'garden'
consists of a 4x4m patch of "grass"
snip
The "grassed" area consists of nettles and dandelions, with thin
straggled bits of grass at the edges.
snip
'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?

Ask three people and you will get three different answers. ;-)
I had the same problem on a patch very much bigger than yours.
I set to with a garden fork and dug the nettle roots up. Its old
fashioned. It works. I reckon I got 98% of the nettles and docks and
hogweed out. Within the year most of the ground had dormant grass
seeds sprouting. The bare patches were sown with locally mown hay
seed. The benefit of this is that the grasses will be suitable for
your soil type.

Your timing is perfect. Hay should be being mown about now (depending
on your location). Offer to glean your local farmers hay field - he
will probably thank you for the offer. Toss the gleaned hay around on
a plastic sheet, dispose of the hay. Sow the seed. Result? Grass -
hardly a lawn yet, but a thick luxuriant grass sward.

Digging the ground over has the benefit of breaking up hard packed
soil and plant growth is more prolific in open textured soil.

--
ned