It really was as easy as I said.
msg.payload --> markdown node --> template.
You didnt even need to modify the markdown node or the template.
flow
[{"id":"f4977a3a93b687b9","type":"inject","z":"6e46a349d744ceaa","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"true","payloadType":"bool","x":150,"y":360,"wires":[["21f6e9c54ce6aa06"]]},{"id":"21f6e9c54ce6aa06","type":"template","z":"6e46a349d744ceaa","name":"some static markdown","field":"payload","fieldType":"msg","format":"text","syntax":"mustache","template":"| LED # | Event |\n| :- | :- |\n|7|Machine health / Reboot / IP Events|\n|6|Flow error / NTP error / Alarms|\n|5|MQTT comms failure|\n|4|Tablet power status|\n|3|S5 power status|\n|2|HTC power status ** Now used for S21|\n|1|TEST LED (TimePi CPU load indicator) Plant watering status indicator|\n|0|Heart beat|","output":"str","x":340,"y":360,"wires":[["84296c512740e13d","5802bb7dc4a27a67"]]},{"id":"84296c512740e13d","type":"markdown","z":"6e46a349d744ceaa","name":"","x":190,"y":420,"wires":[["aa45155ecf920aca","3d32e9fdcc21eb1e"]]},{"id":"aa45155ecf920aca","type":"debug","z":"6e46a349d744ceaa","name":"rendered","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","statusVal":"","statusType":"auto","x":380,"y":480,"wires":[]},{"id":"3d32e9fdcc21eb1e","type":"ui_template","z":"6e46a349d744ceaa","group":"da0a88142730741b","name":"Table","order":8,"width":"12","height":"9","format":"<div ng-bind-html=\"msg.payload\"></div>\n\n<style>\n table {\n border-collapse: collapse;\n font-family: Tahoma, Geneva, sans-serif;\n }\n table td {\n padding: 15px;\n }\n table thead td {\n background-color: #54585d;\n color: #ffffff;\n font-weight: bold;\n font-size: 13px;\n border: 1px solid #54585d;\n }\n table tbody td {\n color: #636363;\n border: 1px solid #dddfe1;\n }\n table tbody tr {\n background-color: #f9fafb;\n }\n table tbody tr:nth-child(odd) {\n background-color: #ffffff;\n }\n</style>","storeOutMessages":true,"fwdInMessages":true,"resendOnRefresh":true,"templateScope":"local","className":"","x":370,"y":420,"wires":[[]]},{"id":"5802bb7dc4a27a67","type":"debug","z":"6e46a349d744ceaa","name":"raw markdown","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","statusVal":"","statusType":"auto","x":580,"y":360,"wires":[]},{"id":"86d6a8cfac496b83","type":"template","z":"6e46a349d744ceaa","name":"some static markdown","field":"payload","fieldType":"msg","format":"text","syntax":"mustache","template":"```\nLED # Event\n7 Machine health / Reboot / IP Events\n6 Flow error / NTP error / Alarms\n5 MQTT comms failure\n4 Tablet power status\n3 S5 power status\n2 HTC power status ** Now used for S21\n1 TEST LED (TimePi CPU load indicator) Plant watering status indicator\n0 Heart beat\n```","output":"str","x":340,"y":560,"wires":[["c73cff3238ccf17e","606c745dbf2e396f"]]},{"id":"c73cff3238ccf17e","type":"markdown","z":"6e46a349d744ceaa","name":"","x":190,"y":620,"wires":[["76d5060bd3760614","56daaafe09cb47f3"]]},{"id":"76d5060bd3760614","type":"ui_template","z":"6e46a349d744ceaa","group":"da0a88142730741b","name":"code block","order":8,"width":"12","height":"5","format":"<div ng-bind-html=\"msg.payload\"></div>","storeOutMessages":true,"fwdInMessages":true,"resendOnRefresh":true,"templateScope":"local","className":"","x":390,"y":620,"wires":[[]]},{"id":"0d736e43bb17f23a","type":"inject","z":"6e46a349d744ceaa","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"true","payloadType":"bool","x":170,"y":560,"wires":[["86d6a8cfac496b83"]]},{"id":"606c745dbf2e396f","type":"debug","z":"6e46a349d744ceaa","name":"raw markdown","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","statusVal":"","statusType":"auto","x":560,"y":560,"wires":[]},{"id":"56daaafe09cb47f3","type":"debug","z":"6e46a349d744ceaa","name":"rendered","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","statusVal":"","statusType":"auto","x":380,"y":680,"wires":[]},{"id":"da0a88142730741b","type":"ui_group","name":"Default","tab":"c32ef9de44166c12","order":1,"disp":true,"width":"12","collapse":false,"className":""},{"id":"c32ef9de44166c12","type":"ui_tab","name":"Markdown Demo","icon":"dashboard","disabled":false,"hidden":false}]