MohammedLover, it basically comes down to "hope for the best (get there on time) but plan for the worst (expect delays)". Always have contingency built in. Whereas from your comments, you would seem to be hoping AND planning for the best ( "remembered the fastest time I ever made the journey in and incorrectly predict it would be the same again" ). If you think it'll take twenty minutes to get ready, give yourself thirty. If it's a ten minute walk, set off fifteen minutes before. If you're driving, remember you have to find a parking space (and finish the journey on foot), and that there may be roadworks/diversions/traffic jams.
Look at some of the things you've said :
- I am very likely to have counted backwards incorrectly the time I need to set off
- or underestimated how long it takes to get ready.
- Or relyed on the satnav version of a journey time
- or just remembered the fastest time I ever made the journey in and incorrectly predict it would be the same again.
- it was me messing around before leaving the house that really made the difference.
These are all things that can be planned for - and 'planned for the worst' for 
! Double/triple check your time counting if you've got it wrong before. Build contingency (urgent loo trip) into your estimates of how long it takes to get ready. Don't assume you will match your 'record journey time'. Remember the SatNav knows nowt about roadworks or congestion.
"I like to arrive calmly and without the sweat of there not being a car parking space close by but usually the early birds have rocked up and walked a short distance and had a wait while I walk hurriedly the 3 blocks back from the only car parking space left in the neighborhood."
This is the result of not planning for the worse. Not only were you not an early bird who got parked more easily, you hadn't built in the contingency of having to walk from a far space.
"Socially it is harder to make small talk when arriving early and waiting with a gathering group it's far less stressful arriving once things aren't so stifling."
If your contingency gets you there in plenty of time, you don't have to be early. If you're parked up with ten minutes to spare, listen to the radio or take a slow stroll to your meeting point. Go to the loo and comb your hair. It's always better to waste a little time calmly at the end of your journey than to eat into the time you need before setting off.
"I find it particularly demoralizing when I've been on time but the other person is early so they moan for keeping them waiting then to be told you are 'always' late when this is not factually correct."
It may not be absolutely factually correct, but you yourself say that you are 'often' late; it is therefore that person's perception of you, as a latecomer. If they moan, just calmly point out that you are on time THIS TIME. Once you've done it often enough, their perception may change.
"Have you all got a good awareness of time in general, is there something lacking on the part of the late comers?"
I don't have a particularly good time-sense. Without a watch on my wrist I am lost. There are clocks in every room of my house, and the radio is on pretty much always, which gives me regular timechecks. If I have somewhere to be at a particular time, I just leave loads of contingency and get as much preparation (clothes ready, route planned) done the day before as I can. Planning for the very very worst !