Hi
In Joomla, if an article or category does not associate to a menu item it will use the ID of that item in URL.
http://www.al-ikhlaas.org.uk/72-welcome/523-school-welcome
72-welcome Category name with id.
Create a new menu with type category blog and select this category. so when you open the articles under this category it will open under this menu.
The article id will be removed when you have a menu with type single article and select this article.
Because in Joomla article id will always show for articles.
You can use 3rd party extension to create custom URL name.
Regards