The green growth in the last picture is unrelated to the corms you've found - they are Crocosmia, a flowering plant with narrow, swordlike leaves, and this string type arrangement as they multiply is typical. If you want to replant some, do not separate the strings, plant them as they are.
It's impossible to know whether the corms are Crocosmia masonorum, the basic, short stemmed orange flowered type that grow wild down in Cornwall and Devon, or whether they are one of the newer, taller and more attractive hybrids such as Crocosmia 'Lucifer', which is also known to be invasive in some soils. I suggest you dig them all out, then put a few in a deep pot in potting soil and wait and see what develops when they flower around June or July. If you like them, you can replant once you know what they are. There's no point in keeping all the corms, there will be far too many anyway, and if you decide to keep the ones you've put in a pot and replant, they will multiply all over again over time.