Thanks @borpin ; I have finally managed to get it to work - and for the possible benefit of others following in the future, this is what I needed to include…
sensor:
- platform: emoncms
api_key: XXmyAPI_read_key_redactedXX
url: http://192.168.1.150/emoncms
id: 1
unit_of_measurement: "C"
include_only_feed_id:
- 106
For me, the inclusion of the trailing /emoncms made all the difference.
Yee Gads, this is all very exciting when I get it to work