Pretty much what "hammertime" over on that forum advises, get the codes read on some decent diagnostic equipment. Phone round for best prices, does not have to be a Vauxhall dealer, lots of places can do it, but make sure you tell them you need the ABS codes read too, as cheaper systems cant do this.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix cars.