If I want to change ablock title - like Ads (search) for example, how do I do it?
 
Mybe I am being stupid but I can't find anywhere to change the default block titles...

Hi there,
You can change it in viart messages straight from Admin.
 
admin/admin_messages.php page.
Search there words:
SEARCH_TITLE
Ads
 
and change their values with your new words.
 
Other way is to change this in static way e.g
in file /templates/your_template/block_search.html
 
Attention: block_search.html is template for products search block and ads search block too. So if you change title manually you'll change them both. For product search block and for ads search block.
 
Template "ads_search.html" is whole page template not block template.
 
Hope it helps.
Cheers
Neosim