I just wanted to come back and say a huge thanks to you.
You are right, I couldn’t access the queue debugging page, even when bumping up the available memory and execution time (nightmare!), so I have removed the batch rows directly from the DB and the whole site is back to running smooth as butter.
Also, well done for spotting that we have an external feed, I understand how this plays havoc with the plugin. For the moment, we have disabled the plugin so as not to end up in the same situation until we have done some testing.
You, sir, are a superstar! Thanks for your great support.
Thom