I can understand your frustration.
Let's assume for the minute that the netbook is damaged by liquid ingress.
You'd expect a communication from the service department advising that this is the case and explaining where the liquid has entered, what the damage is and your options. i.e. the cost of repair is not covered by the warranty, but it can be repaired for X pounds, is not repairable or whatever.
It's this lack of clear communications, coupled with a fault report sheet that doesn't provide any confidence that it relates to your machine and the shrugging of shoulders when you return to the store that makes the blood boil.
I think DSGI still have some way to go on the customer care skills.
I don't know the cost of the product and it's relation to how much it would be for an independent repair facility to confirm and or repair the fault. You should however be able to recover this cost if liquid ingress is proved not to be the cause of the problem.
My own experience of working in a service industry for 30 years is that many items are indeed damaged by liquid ingress and rarely if ever was this admitted by the customer. They may not even have been aware of the fact as a tiny amount is sufficient to corrode fine print on a circuit board.