"Tumbleweed" wrote
snip
BTW I am currently also getting lots of acorns sprouting in my garden,
including the lawn, but there are no oak trees within 100 metres or so.
What would plant acorns in the lawn? Squirrels or something else? Last
year I found a sprouting acorn in a hanging basket! But I have only ever
seen one squirrel in my garden.

Could well be Jays. They collect several acorns at a time in their crop and
then hide them elsewhere for later retrieval. In recent Autumns I've often
seen them poking around in the grass down in my wild bit, then every Spring
I find little oak seedlings popping up in odd places, so they obviously
don't retrieve them all!