Spamnophobic, you've set me on the right track. Outllook 2007 does indeed have profiles as you described. However before I set them up, I thought I'd seen something similar.
I set up all email accounts, both spamcop and the others in the normal way in outlook using the smtp and pop settings for each unique account.
Then select Tools > Send/Receive > Send/Receive Settings > Define Send/Receive Groups.
The default group is called All Accounts and it sends and receives from all email accounts.
Set up another group for receive only, deselecting the ticked 'send mail', and add spamcop account to it so it receives only.
Go through all the other accounts in the 'All Accounts' and untick the 'receive mail' for them.
So you have one group to send mail, and another to receive mail just as described with profiles only this is within Outlook.
I'll monitor it for the next few days but that would appear to be it.