I've recently gone through a range of upgrades, including the Xtreme Core, Aluminium upgrades, carbon boom, Xtreme180motors. I have now decided to go back to the stock set up until I can figure out why I'm not getting any height.
This is a fairly recent problem but I notice that I'm just not getting the same "punch" when I apply throttle. Previously on application of throttle the heli would jump up into the air, not anymore!
Brand new batteries, brand new Xtreme 180 motors, new blades, etc. The only thing I can think of is the 4 IN 1 CONTROL UNIT. Can this unit degenerate over time (set up is about year old)
Everything functions normally, movement of swashplate etc. but heli flies only to a height of around 5 feet and I can't get any more lift.
Any suggestions from you pundits out there, I've tried everything I can think of and the only thing which hasn't been replaced is the 4 in 1.

Have you tried an [link=http://shop.boomtownhobbies.com/product.sc;jsessionid=3552252079DE0862FC023C771DDE 2E42.qscweb23?categoryId=2&productId=14]Upgrade Battery[/link] that provides more power for your new extreme motors, also make sure that your gears are not binding with the new motor instalation.

Depending on how heavy your bird is with all the upgrades that is most likely the root of the problem! I have a fairly heavy CX2 with all my upgrades and the stock lipo's don't perform well at all. However with the added punch of my higher C rated lipos she is alot of fun! I would say seriously look at better bats and that should solve the problem.

What kind of blades are you using? Stock e-flight? I've had problems with bad warped blades where my heli only had about 3-4 minutes of flight.

test your blades for me.

Eat2muchrice’s Warped blade test
http://youtube.com/watch?v=_7PwNTXOWMs

Eat2muchrice’s Blade boil fix
http://youtube.com/watch?v=RmNv8OlG6GQ

I had the same issue with height and it wasn't in any of the upgrades, it was in new but bad blades. I would pull off all the blades and make sure they are good blades [link]http://www.youtube.com/watch?v=_7PwNTXOWMs[/link] if they are bad then try this [link]http://www.youtube.com/watch?v=RmNv8OlG6GQ&feature=related[/link] hope it helps but also it could be that the outer shaft collar is on too tight it needs about 1 paper width of play from what I hear

beat me to it eat2muchrice =)

Thanks guys for all the contributions, let me tell you where I'm at now.
I have taken her apart completely and re-assembled with all the alu upgrades which include, swashplate, alu lower rotor hub, longer inner shaft with alu upper rotor assembly (I'm getting so good at stripping this thing down and re-building I can practically do it with my eyes closed!)
Stock e-flite blades.
Batteries are brand new and include both the stock e-flite battery but also the new Flight Power Evo battery.
Flew her just now and from a freshly charged battery she flew like normal for all of 5-6 minutes then lost altitude and hovered just a few inches off the floor. No sound of loss of power from motors or anything like that, ergo batteries are ok!
On full throttle she still continued to hover a few inches off the deck but failed to gain any altitude.
Landed and rested for couple of minutes after which she flies again like normal but for less then a minute then back to hovering just inches off the deck. Repeat the rest period of a couple of minutes and she takes off again like normal.
I'm totally bamboozled.
Also, have changed blades repeatedly so don't reckon it's in the blades, hence the reason I come back to the 4 in 1 unit. Could this be past it's sell-by date and perhaps overheating and not allowing sufficient current to pass to the motors (I'm no electronics expert by the way) and since I've tested/renewed just about everything else this is the only conclusion I can draw.
What do you think?

Could be, I have read other posts on overheating, some people took the unit out of its plastic casing to allow for better passage of air.

I would still check the blades. I've spent two weeks trying to fix my heli once and it turned out to be warped bad blades. it was 3-4 bad sets out of 5.
check it again.