I have probably 12 Broad-leaved Helleborine in our garden. One appeared between 10 and 12 years ago. Since then the numbers have increased annually without any conscious assistance on my part. This is the 2018 photograph of the original plant which has grown stronger each year.
They appear spontaneously in cracks between walls and the tarmac drive; in beds and borders, in shade or in sunny places. And I have been delighted that they have thrived here in our garden in Eastcombe (GL6 7DW)
We are both members of the GNS (my husband has been a member since 1984) and attend the Cirencester winter meetings and occasional field meetings in the summer.
I hope this report is of interest.