bedtime problems

Hello,..I only have my adorable little guy 1 week--he's 11 weeks and from a litter of 6, the home he came from was excellent-the owner did tell me he's a bit "clingy" which I just about manage during the day but nightimes are just hell. I dont want to give him the habbit of sharing our bed-though one night in deperation I did!-he sleeps in the kithen-the usual tricks, hotwater bottle, clock, his mothers scent from blanket-etc but as soon as I close the door it starts--the whining and howling--last night until 3am--he does it during the day too when i leave him alone but as i say I can manage that----what I'm worried about is could the nightime horrors for him damage him? I realise i have to let him know "who's boss" but is there an easier way?
As far as toilet training is concerned he nearly has the message and likes to "go" outside and has nearly started to "ask" at the door-as few accidents but for 11 weeks he's excellent. I would be grateful for any tips please---you have a wonderful website--thank you--Coogee's mum