[Casey76]

So how many, or few, seed potatoes would I need for 1 four or five metre (15 ft) row?

I'm only growing for myself, so don't want to swamp myself!

I'm just a bit concerned that I'm only going to need a few, when they are being sold in boxes of 40, 60 or 100!

[mumofstig]

You only need to plant one every 15-18 ins so only need about 10 seed spuds
( perhaps a little closer if they are early types when you may get 12 or 13 in the row  )

[m1ckz]

i plant my earlies about a foot apart..main crop about 18 in 

[3759allen]

i plant my earlies about a foot apart..main crop about 18 in

same here

[Casey76]

Hmm... The smallest packets I've seen are 20-25 and the choice is very limited.

Still, I suppose for an experiment, a waste if 5 euros or so isn't too bad

[DD.]

Plant all 20 in that row, then start harvesting every other one, return to the start of the row when you get to the end.