BMW 323ci cracked head

[DaveW320ci]

My girlfriend has a 2000 BMW 323ci convertible with 40k on the clock. The car is just 2 months out of warranty and the head has a 4inch crack.
The oil levels have been falling for some time ( probably within warranty period ) so problem started in warranty. Unfortunately she has no proof and BMW are asking for £1200 towards the cost of labour. Are there any known problems that could have contributed to this?
They say it could have been caused by overheating but hasn't overheated once ! Thermostat problems may have masked this !
Can anyone offer any advice as BMW UK aren't being helpfull and say she has just been unlucky ! Could a manufacturing defect be more to blame or overheating?

[AUSSIETECH]

Your right a broken thermostat could cause the vechile to over heat!!
but should have been noticed as an irregular temp gauge often occurs.
Your oil consumption problem also should have been reported to a dealer so dignosis could be made .
If the vechile hasnt had a history of being serviced at a dealer your chances of a good will claim are slim but if u haggle at them enough they might come half way with labour or somthing but your chances are slim .sorry !!