my mg zs will not go over 5000 revs when driving but when stood still and not in gear it will rev right up to the top i have just done the head gasket any help would be gratfull .

Sounds like maybe you havent allowed the new HG enough time to bed in, and the car is losing compression on full throttle.
Its always a good idea to drive like a granny for the first 1000 miles following an engine stripdown - ie a running in period. I've just done my head gasket, and am not giving it the revs till its done at least 1000 miles.

wont rev over 5000 when in motion? sure you've not got a stuck brake?

if you drive along dip the clutch will it go over 5000 then

Hi, when you say the engine will not rev over 5000 rpm under load, is that in all gears or only in 5th?

If the engine starts OK and since you have just renewed the headgasket it might be worth rechecking the cambelt timing again which might be a tooth out of sync.

sorry its an auto box double checked the timing marks and they all line up and checked the brakes and they are fine i did have to re do the auto tensioner on the cambelt again

I take it its the Steptronic CVT box then - if the revs are limited to 5K, then maybe there's a problem with the auto box - is it not linked to the throttle potentiometer? when the car was put back together, were all the connections put back on properly, and was the throttle pot initialised by pressing the throttle to full power and back 5 times when turning on the ignition?
Maybe its just a stab in the dark, but CVT boxes dont always allow full revs until the fluid in the box is at operating temperature (I used to have a Nissan Primera CVT) and it wouldnt operate the lockup clutch either until the box was warmed up.

I have a CVT and I know it revs up to the redline in Neutral. But in drive, most I have ever gone up to is 5500 revs. Since by the time you have reached this and try to really exceed this rev, then you are doing plus 70 anyway which is illegal. Put it in L or the equivalent, what effect does this have?