I would like my game end screen credits to scroll, rather than dumping it all in one block, is there an elegant way of doing this other than inserting delays in between 'print message' commands?

Typewriter function???
Don't know, haven't tried it...
But it does sounds cool!!!

Maybe not quite what you want, but you could set up a timer that will print a string from a string list every 10 seconds. Say the string list is in game.credits, the code for the timer would be:

if (ListCount(game.credits) > 0) {
  s = StringListItem(game.credits, 0)
  msg(s)
  list remove (game.credits, s)
}

Alex did some pretty smart text effects in his game Moquette using JQuery; he explains some of it here in this blog post:

https://blog.textadventures.co.uk/2013/11/26/building-moquette-simulating-the-london-underground-and-doing-pretty-things-with-text/

I know JQuery has scrolling text effects - if you can work out how to implement it.

You can play Moquette here:

http://textadventures.co.uk/games/view/zbzfpcnknu_vdjog-cbihw/moquette

I used the Typewriter function DarkLizerd is talking about. But I would suggest only using that for short sentences as it puts a 'block' of text which doenst add to readability.