In my personal car about £60 per month in diesel - only gets used at weekends. My work van ranges from £200 - £400 per month in diesel depending on travel (paid for by work obviously).
2cars, majority of use is in 1996 320 touring, with the mrs using my derv powered 9-3.
Between the 2, with an average of 1200-1500 miles a month, I would suspect Im putting somewhere between 200 and 300 english pounds into the Shell garage each month