Starting late or ending early for Summer Internships?

Does anybody know the policy of most consulting firms on either starting summer internships late (1-2 weeks) or leaving early (2 weeks)?

I go to school at a target in the US but am currently studying abroad in the UK, so I could either apply to the London or US offices.

The problem is, classes in the UK go until mid-June, so I would presumably miss the first week or two of the internship (could try to leave a week early from school but that's not guaranteed) if I go to any US office. Or, I could apply to the London office and start the 10-week internship in July on time like everybody else in Europe, but I would have to leave 2 weeks early because my Visa expires mid-August, and the internship lasts until the end of August.

I'm really not sure what to do in this situation, and deadlines for all the UK internships are around November, versus Jan/Feb in the US. Has anyone experienced this before or know what would be the best thing to do? I'm shooting for MBB, OW, Booz, Roland Berger, Deloitte, and Accenture.

Thanks so much!