I've come back to Quest after several years
I'm not tech savvy so bear with me..

The scripts aren't running at all - i.e. when I select 'expression' as per the tutorial there is no drop down, and sometimes a condition is generated i.e, sometimes not. For example, I can select the 'If' command, but when I select expression I just get a blank box or an incomplete condition with no options?
I think this is a bug as I can't work out what I'm doing wrong? I don't think I'm meant to manually insert the condition?

when I select 'expression' as per the tutorial there is no drop down

What drop down should there be? Select 'Expression' and type in any expression you want.

If you want to choose one of the preconfigured options, you need to choose that instead of 'expression' (although I think that choosing one of them and then changing the type to 'expression' will let you see the expression that represents that condition)

I just want to run the same basic 'If TV switched on' condition that is in the tutorial.
As far as i can tell if I select the 'object switched on preset then I shouldn't have to manually enter code to complete the condition ('then' etc) or should I?

I shouldn't have to manually enter code

You said you are choosing "Expression" - that means manually entering an expression (a little piece of code)

If you don't want to enter an expression, don't choose "Expression"

Right so you're saying there's no preset expression option. Fine. But even still using this:
http://docs.textadventures.co.uk/quest/tutorial/using_scripts.html

If I follow the steps and select 'if object switched on ' then object 'tv' I am not getting a 'then' box so I cannot complete the command.

That certainly sounds like a bug.

Are you using the desktop or web editor?
Can you share a screenshot of what it looks like for you?