Bluebell
Like Don, I plant potatoes at rather higher densities than you’re suggesting.
I go: 30cm within row and 40cm between rows for 2nd earlies; 40cm within row and 50cm between rows for main crop. My ‘rows’ go across a 1.5m wide bed, so they have either 4 or 5 tubers per row.
For both I get around 50lb for 3 square metres sown. I’ve had higher for main crop, but not consistently to date. You may not get that much on a new plot…..
By doing this you get a very dense foliage which pretty much eliminates weeds.
I also ‘hill up’ using a combination of grass clippings, comfrey leaves and compost/manure, which helps to create a great tilth within 12 months of sowing your potatoes.