In message , Jimk
writes
Graeme Wrote in message:

I imagined cutting into the lid against the existing rim, such that the
lid would come out leaving the rim in place.

With some scrap timber to level it up for your jigsaw cut?
Still be a nasty edge to navigate/deal with...

Indeed. Perhaps make the cut 1/4 inch or so in from the rim, then go
around the edge with tinsnips, cutting from the edge to the rim, then
bashing the 'petals' downwards with a heavy hammer. All a bit long and
drawn out, but better than lacerated fingers.

Thanks for all the comments, which have made me think beyond the
obvious.

--
Graeme