I assume the aerial goes to the Humax and then to the TV. If this is the case disconnect both leads from the Humax and connect them together; that takes the Freeview signal directly from the aerial to the TV. Now re-tune your TV and then see if you can get BBC1 etc. If you can't you might have an aerial problem. If you can it looks like you have a problem with the Humax box.
If you've connected the aerial directly to to TV, retuned the TV and cannot get any programmes then either you have an aerial problem or your TV has gone faulty. It's difficult to make any further suggestions so I think you might have to call an engineer in.