I'd be surprised if they would add it all to your salary, as they likely rely on a certain percentage of employees not fully utilizing the benefits--much like insurance. But it never hurts to negotiate.

School fees at a British school run at about 30,000 plus per student; a car probably cost roughly 20% more to run than in the UK; housing varies, but including utilities is about 10,000-25,000 depending on location and family size. Home leave is usually one business class fare for each person. There are other benefits that employers offer, too, depending on the employer and position--professional development, communications allowance, etc.

Good luck.