There are many models of the Hoover Telios. This solution applies to the T5603 at least, but perhaps not to all models... sorry, I don't know about the others.
Anyway, this is it. The cover is held to the base by 8 screws. Two are clearly visible near the handle, two are in the bag compartment. They are easy! The problem is finding the others, because they are concealed by the foot-operated switch plates, and you have to get those plates off without breaking them.
Basically, those plates slide off backwards (i.e. away from the handle end) but you have to release a plastic catch first. The catch is part of the switch-plate, and is located roughly mid-way along the straight side of the plate, just by the raised bump. You can just see the catch if you shine a torch light down the gap. The catch is released by inserting a small screwdriver or other flat blade and levering it away from the centre-line of the machine. If you apply gentle rearward pressure on the plate while doing this, you will soon feel when it's released.
Once the catch is released, the plate will slide off completely and the remaining four screws are revealed. After that, it's simple!
Hope this helps!
2ndKnight
July 2009