Hi - further to brokentelephone's recommendation, I heartily suggest Trishna for Indian and if you can arrive before 7pm today, they have a four course menu for 20GBP. It is great value. It is my favorite place in Marylebone and on a short list of my favorite places in London.

If you like digestive crackers for the base of your cheesecake, more power to you. However, the fact that you say that digestives are good with butter and cheese on them does indicate that digestives are not the same flavor profile as graham crackers. Doesn't mean digestives can't be used, just that the taste won't be the same. If the poster's friend makes traditional American cheesecake, she'll want to tuck a box of graham crackers in her suitcase.

If your friend bakes cheesecake, she will need graham crackers / graham cracker crumbs. Using tea biscuits is an unacceptable substitute.