Sowing Green Manure seeds in the now empty potato patch

There is an area of the vegetable plot that was used for the first earlies and is now cleared and empty. All gardeners know that a empty bit of land is an invitation to weeds to begin to grow and take hold. The old saying about leaving weeds to set seed and you will be removing them for the next seven years has more than a grain of truth in it. That leaves the question what can I sow in this fairly large patch of earth?

(I will be sowing lettuce and other vegetables such as carrots (certain varieties can still be sown) in other spaces on the vegetable plot.)

In the place where I had my first early potatoes I am going to sow a green manure crop and then
turn it in to the soil later on, this benefits the soil by adding humus as well as having the benefit of giving the weed seeds a 'run for their money' by blocking out the light and giving them a bit of competition. I need to check on which green manure seeds I will sow, as different seeds suit different soils, seasons and benefit in different ways. For example a few years ago I planted mustard as that is supposed to help clear the wireworm problem from soils. No need to plant that this year as that was not a problem for me, just luck, or the earlier years green manure mustard seed i have no way of knowing. My first instinct is to plant Phacelia as I find it easy to grow and like to leave a few for the bees. As I said I need to do a bit of research before I order the green manure seeds and sow them.