golf 2.0 ltr gti, 54 reg. - water loss - wattie
only half the message did not go on first time, a friend flushed the system out and filled it with the correct vw g12 coolant,on inspection at first there was no signs of a leak any where, the reason i asked my friend to have a look was because after the first top up the water in the expansion tank was a dirty greyish black, but when it was flushed through there was no signs of any dirt, only done 63,000 miles, there also is a lack of oomph that was there before, any ideas people.
golf 2.0 ltr gti, 54 reg. - water loss - tdc

Sounds like engine oil contamination of water suggesting failed cyl head gasket.A compression test may show up the offending cylinder.Check dipstick for any oil discolouration if losing water too.

golf 2.0 ltr gti, 54 reg. - water loss - Peter.N.

That would also account for your loss of coolant. Look around the filler cap and overflow pipe for signs of dry antifreeze. If you place the end of the overflow pipe in a receptical you will be able to see if its being blown out.