Have you considered the name LAIDMAN as a variant of yours? I am conducting a one-name-study of LAIDMAN (and variants). I must say I have not come across Leddiman. The Laidmans came from the north of England, but there is a substantial London branch who arrived in the C18. However, no Leddiman spelling amongst them. Still, you never know - it would be interesting to discover the variants that DO exist for Leddiman. If you do manage to go back and land up in the north of England, please let me know as we may well have a lot in common!