I have the same problem with my dog although chewing in the house has now stopped. Although it didnt stop until he had had a nibble of everything!!, i even have holes in my walls!!!!
He has now started to steal things shoes, tea towels, toilet rolls, remote control, MOBILE PHONE. I know why he does it, he does it as he wants me to chase him!!!! Why? i dont know???
Last week he stole one of my cushions off the settee, nothing new there, he ran through the house and straight through the dog flap into the MUDDY garden with my WHITE cushion!!! He tends to do it when i am doing something that does not involve him ie ironing, cooking etc. As i know he is doing it for attention i try to ignore him, but then he brings the item he has stolen and sits in front of me so i cant see anything but him!purposly trying to get my attention. Our trainer too said it is boredom but he did it yesterday after an hour and twenty minutes walk round the lake, swimming etc, then a game of ball when we got home and then a game of find it. I have come to the conclusion that he needs an awful awful lot of stimulation.Perhaps if i am totally honest more than i can provide him with. I do try my best. He receives a total of 2 1/2 hours a day of one to one ie walking, playing etc, more at weekends. He has two walks a day sometimes three. I tend to take him on a long walk on sundays somewhere different each time.
He has every toy/chew i can buy.
I think some dogs, especially cockers are very hyper. I have tried everything with billy but he is still as energetic and mischevious!!! i am constantly being told by his trainer to have him castrated. Not somehing i want to put him through.
I wouldn't worry but just try and think of how you can make life more interesting/challenging for him. Make him work for things instead of handing them to him. For example every morning i used to give Billy his breakfast in his bowl and then give him a dentastix straight after. Now he gets half of his breakfast in his bowl and the other half in a treat ball. It is a ball which you put food into and as he pushes it along the floor bits drop out. So he has to work for it. Then if it gets stuck somewhere, behind the settee etc he has to work out himself how to rescue it. Billy absolutley loves it. Then when it is dentastix time he has to go out of the room whilst i hide it! Then on command he has to come in and find it. He loves it the only problem that i have is he drools all over my carpet whilst trying to sniff the treat!!!
Billy needs mental exercise as well as physical otherwise he is a real real handful. I do believe that he is more hyper than a large majority of dogs but i have accepted that that is the way he is. I would try some of the things i have mentioned and others have before you reach the same conclusion!! Good luck!!