Once the pup has settled in, I would begin to leave it for short periods to get it used to me not being around all the time.
I wouldn't leave a dog from 9am...5pm at any age really..they are pack animals & it would distress most dogs to be alone all day everyday. Personally I would be happy to leave a puppy of say 6 months, at home in a safe environment for up to about 4 hours after I'd walked it & let it go to the loo. At about a 10 or 11 months I'd extend the time a little if necessary..but I don't think I'd ever be happy to leave it all day. It's only my opinion tho.
I work in a dog creche where people bring their dogs for the day when they're at work. I personally don't think there is any harm in leaving your dog alone, you don't want your dog to become clingy. Your dog needs to be well socialised from an early age so it doesnt' become clingy, but i dont see anything wrong in leaving it, once it has got used to its new home
In reference to you working in a dogs creche, do you know of one in Jersey (Channel Islands?), how much does it cost to leave the dog all day 5 days a week?