Run using something like:
while sleep 300; do ikeacheck.sh;done
to run a check every 5 minutes. The script notifies you via notify-send. and puts a timestamp in ~/tmp/ikea.txt.
The curl command is stripped for reference here. To get the exact command, fill the PIN code form at the bottom of your shopping bag, open network tools, and capture the request made to
/clickandcollect/in/receive/. Right click and "Copy-to-curl" on that request.
Once this succeeds, your account is added to the list, and if you open your browser sesssion again, you should'nt get the 818 error.