Cheers Gaz D - I'm getting a better picture of what is required....and I'm beginning to think I'm still a way off

I can tell, from the posts and videos that I've got to be able to hold my breath for much longer! At the moment I'm descending, then I only have about 10 seconds before I have to return to the surface! Not a lot of time to 'hide'!

I can hold my breath out of water for like 2mins...but by the time I've descended, I've already used a fair chunk of my O2 reserves! (Must get fitter!)
I feel I'm under-weighted as it's slightly tough to get going down without spashing the surface (and feels like a little too much effort but could be technique) but I've read the dummies guide (here on DB) and
after exhaling it says you should be buoyant on the surface...I'm 'buoyant' but nose&mouth under water (which for SWB isn't too useful) so I'm figuring I can't be under-weighted (if anything still overweighted!). If you guys exhale at the surface are you buoyant to the point that your nose/mouth is out of water? I've got a 5mm wetsuit+boots (no integral hood) and I'm carrying 7Kgs of lead....Sound about right?