I am installing a new kitchen.The hob is to be ventilated with a B&Q supplied 'Marley' 5" vent kit.When I was unpacking this kit I dropped the wall grille and it broke.It is quite flimsy.Try as I might I cannot find a replacement for this grille.It for 5" flat profile ducting with a rectangular spigot.Can anyone tell me where I can get a such a thing as I do not want to go to the expense of buying a new kit.