I seem to remember having a lot of trouble with the installation (probably mainly due to my inexperience) so I fumbled through a lot of trial and error and searching online for command line examples. I know I definitely ended up doing a LAMP installation. I wish I’d known there was a simpler route! 
I’m very wary of touching it at this stage as it’s all functioning. The only reason I’m tinkering now is to update the expired SSL certificate but can’t seem to get past this error.