Domain's menu not available to 'basic page' when using 'provide a menu link' function.

hi @agentrickard, thanks for replying - yes each menu is populated with links that point to pages only available on the same domain.

Hi again, I think I have found some reasons for the behaviour described. What I think is happening is the following:

Each content type has its own 'Menu Settings' where the user can select the 'Available menus' for that particular content type:
http://www.example.com/?q=admin/structure/types/manage/[content-type]
I had left this as the default, i.e. my default domain's main menu was the available menu for my basic page content type (which explains the 'Problem' outlined above)

Any changes here override the settings on:
admin/structure/domain/view/[current-domain:id]/config
On this page, I edited the content type's menu settings, i.e. 'Basic page menu settings' and under the 'Basic page: Available menus' ticked the checkbox relevant to my subdomain.
I have also, under 'Menu Settings' on the same page, selected the relevant subdomain menu as the 'Source for the Main links' and 'Source for the Secondary links'.

I would have thought that perhaps on http://www.example.com/?q=admin/structure/types/manage/[content-type] there could be a way of specifying that the 'Available menu' could be the users 'Current menu' or the main menu specified for the active domain. Or maybe I'm missing something?

Anyway, knowing this goes some way to solving the problem, however it implies that one would have to set all domain menus as 'available menus' on the content type and having to update each time a new domain is created. Also, leaving all menus available on all domains when assigning a menu place on the content type makes it more likely that a user could accidentally drop the content into the wrong domain (I have nearly 100 domains and more menus!). Would anyone have any ideas on a way around this scenario?

p.s. thanks again for this amazing module...

Thanks @agentrickard for your reply. I wonder if you know of a way of 'restricting' the choice of menus available when a user creates content e.g. a new basic page, and wants to add that page to the menu (using the Menu settings > Provide a menu link option) so that perhaps he or she can only add the new page to their assigned domain? If this makes sense...
thank you
A~

Thanks @agentrickard - I think you've identified the problem. I don't seem to have this filter to only show menus "that are visible on the current domain". Altering the menu settings on the domain, to 'set a source for the main links' has no effect. Even setting a default menu for a content type on the domain settings makes no change. I wonder what I'm missing?
Unfortunately, using a form_alter is beyond my coding skills at the moment. Although I did find the code below on stackoverflow (which I haven't tried yet). Is this the kind of thing you were suggesting? Can it be added as is or do I need to make any edits, to e.g. 'MYMODULE' (as I said, coding is not my thing - yet! Willing to learn...):

function MYMODULE_form_page_node_form_alter(&$form, &$form_state) {
  global $_domain;
  if (isset($_domain['domain_id'])) { // only display domain's primary links
    $menus[domain_conf_variable_get($_domain['domain_id'], 'menu_main_links_source')] = $_domain['sitename'].' Main menu';
  }
  if (isset($menus)) {
    $options = menu_parent_options($menus, $form['#node']->type);
    $form['menu']['link']['parent']['#options'] = $options;
  }
}

thanks again,
A~

Edited previous post to add code snippet.