I think 'being late' in moving is bollocks to be honest.
Yes, we don't buy players at the start of a transfer window, but the singing of a player is the very end of a transfer, theres much wrangling before then. I suspect O'Neill/Villa may be guilty of being a bit of a hard man to win over in terms of fees and cash, he only seems to pay genuinely big money for players he seems exceptionally keen on, Milner for instance. I suspect in some way that may be down to the budget he has, I've always felt that O'Neill may have been given a finite amount of money for a set period and he's had to spend to a limit often, as well as try to drag the club up and bulk it out, hence his squaddie signings and short term fixes he's often gone for.
I also suspect that we play a waiting game to see others show their hand because of this - we don't want to show our own hand on players we don't intend to get into bidding wars on. Sometimes that may be unavoidable and again, that'll draw things out, especially as the club has a few things it can't escape from, like being in Birmingham. We prefer to wait and see what other clubs may do and jump in late on with firm offers.
Of course, I can;t prove any of that because I'm not Randy Lerner, Paul Faulkner or Martin O'Neill, but it seems to make sense and doesn't just say 'Oh, MONs a slow coach', which to my mind would about the least logical thing in the world to be as a football manager.