I can relate to what you're saying. Recently purchased a used car from a friend, faced the same issue. Then I got to know about this place at Andheri-Kurla road called Motoshines. They are brilliant with what they do.
You should go for an interior detailing service. They clean it really amazing machinery and techniques, makes it look as great as new. Won't have to visit for a year after that, trust me.
Try their website (www.motoshines.com) for starters. Totally worth it and not too expensive.
Hope it helps!