Is there any way to tell App Manager when I want it to check for updates? It manages to swallow almost half of my daily data allowance by insisting on doing it during working hours!

If you have a limited data plan your best bet is to set ur connection to always ask and update it manualy when u need to

That would drive me nuts! Seems a bit crazy that you can't specify something as simple as this. Guess I can live with it as is though.

on the same note, you should see that when you go roaming it managed to eat up 6 megs of data (roughly 40EUR) the first minute i got off the plane at 8:30 in the morning, and turned the phone on. if you go roaming make sure you turn off all repositories so it doesn't have any reason to check for updates.

Not sure I trust this phone enough to roam with it! I have more reliable options when travelling!

Here's the solution:
Wiki page.

You can set a custom interval for auto updates, or by setting a huge number, disable them entirely.
You could still update manually with the app manager (or apt-get) if you want to.

How is 1440 a day?
Would be usefull to know what the units here are if you want to set a custom timing.

24 hours * 60 minutes!

ie it's in minutes!

Thanks Venemo. I presume the clock restarts if/when I update manually!?

If so this is closer but still not quite the solution of setting a time to update!

1 day consists of 1440 minutes.

Yes. If you enter a large enough number there, it updates in those intervals.
If you update manually once with App Manager, the "clock" restarts, and the next auto-update will be after that time plus the specified interval.

If you are concerned about the data costs, enter an absolutely huge number there, and thus "disable" the auto-updates.
Then, if you're on a home wi-fi or something, you can press a button while you eat or work, or something, and the N900 will happily update itself manually, without bothering you.

BTW, there is a "Thanks!" button. :P