It’s not a short commute and quite expensive with season ticket and parking but plenty do it. From Buckingham, your best options would probably be Leighton Buzzard or Bletchley into Euston. There are direct trains from LB which take around 35 mins. stopping at all stations ones that take 50 mins or so. You can park OK at LB although gets quite full by 10am or so. Bletchley is next station up the line so takes longer. Very heavy traffic into Aylesbury in the mornings and the train to Marylebone takes around an hour so much less convenient.
