Drop-down menus

This may not be specifically a WPMUDEV Issue but as all the examples from the 133 pack that I've tried so far don't seem to allow a custom menu and I can't get custom menu dropdowns to work properly, I am asking for advice. The issue occurs both in multisite and single site installations.

With the default menu, defining pages with parents works OK. (I had to move the plugins directory to check this and then moved it back). But of course in many instance I don't want to show all pages so a custom menu is indicated.

The 133-pack themes I've tried don't include the facility to use custom menus - at least not without hacking header.php. Now I am not averse to writing php or css but I am not confident that any hand-additions would be maintained under updates - this is true whether WPMUDEV or not. It is a question of maintainability.

Where the custom template can be used (for example the default twenty-10 theme), the menu appears as a flat menu with no dropdowns, despite the page taxonomy specified. In other words the custom menu doesn't seem to obey the hierarchy specified of parent page. Is there a trick I have missed?

I have tried various plugins of a suckerfish type but to no avail.

I have tried disabling all plugins but this doesn't help.

Is there a recommended way to get the dropdowns? OR do I have to customise the header.php?