Usually on chimney hoods theres a plug is in the chimney section at the top.
Remove the chimney section at the top and hopefully you will see the mains lead in there with the plug top on it. Check the fuse in there and see what you find.
To remove the chimney you normally look at the very top in the back corner to the wall and theres a screw either side.
Remove these and this will allow you to take the chimney section down and fingers crossed reveal the plug top and change the fuse in the plug and this will get it going again.
Then once its working check the bulbs as you may find one has blown as that's the common thing that happens on cooker hoods is the bulb blows and cause the fuse in the plug to blow as well.
Let me know what you find or if you need anymore info just get back to me.