You won't get a discount cc . A while ago there was a trend to drive round in a 4cab pick up type vehicle scribed with decals etc as these were initially classed as a van which only had a $500 tax on the user. Needless to say the chancellor soon stopped that loophole!
Company car tax is a tax on the user/driver and is paid via your tax return. Ie the value of the car together with its co2 emissions is knocked off your tax free allowances. The company doesn't pay this for you! He may pay you extra money towards the tax but it is you that forks out in the end!
Having had years of c.c.'s the c.c.'s of my engine got taxed so much I gave them up C.C.. Drive your own car and claim 40p a mile tax free for business mileage instead. Only up to 10000 miles a year of course as the chancellor hates us to get too much benefit out of it.