The LSE Stock Symbol "*-STK-SMART/LSE-GBP" does actually work - it appears that the error is generated as it is not possible to download the history.
The following Zorro behaviour then means the script stops:
"If the price history of some assets is not available or can not be downloaded, you'll see an error message directly at start and those assets are then excluded from trading. If the first asset is not available, the session will end at this point."
Although this could potentially be overcome using PRELOAD as I am after 1min data that would be difficult. Is there any way of allowing Zorro to just wait and accumulate the required LookBack history before attempting to create the necessary Series for the script ?