Hello, Wulfsige,
I'm sorry if I'm teaching Grandma to suck eggs, forgive me.
I would include other alternative spellings as searches don't seem to include them automatically.
One of my family names is Gilson. I have spellings that include Ghilson, Jilson, and Jelson.
Another is Murten. I have spellings that include Merton, Marten, and Martin.
Errors can arise from misreading an entry being transcribed, or can happen when it is misheard or transcribed phonetically. This is especially likely if the local accents involved are different.
Family Search returns a good number of Jamsons born in Northumberland, Yorkshire, Lancashire and Cumberland in the 18th century.
"Send three and fourpence, we're going to a dance".
Stefan
Stefan