How to get on my PhD supervisor's case without becoming a nuisance? So my PhD supervisor is very senior in the university. This has its advantages but unfortunately this also means he's very busy most of the time, especially now that it's summer and he's been away on holiday a few times. By and large this isn't a problem; I'm quite happy to get on with my work without much supervision. 

The problem I'm now having is administrative. I have a progress evaluation report due and the deadline is nearing (I've already had the deadline extended once). I've completed my section and am awaiting his comments before I can submit (formal procedure). Further, I may need to be moving to another city in ~4 weeks time to work with a partner organisation for 6 months but I do not yet know for certain and my supervisor keeps putting the issue off (this has been the case for the last 4 months).

It's come to the point where these issues are critical, I fear missing the progress report deadline and I need to know where I'll be living at the end of next month so I can sort accommodation.

I've tried sending a reminder email but have received no response. Also, I walked past my supervisor and greeted him but he seemed not to notice me. To make things worse, I don't have the relationship where I can just turn up to his office without an appointment.

I don't really know who I can speak to about this as I work alongside very few people and I don't know what options are available to me save flooding his inbox with emails.

What can I do to press these matters and how can I do it so as not to become a nuisance to him?
As confirmed in a comment, the "very senior" supervisor does have a secretary. I suggest explaining the problem, and the reasons for urgency, to the secretary and asking them for help.

The secretary can go to the supervisor's office without an appointment, and is likely to understand that some university paperwork really does have to be done on schedule. Ideally, the secretary will put together a packet with the partially completed report and any other relevant paperwork, such as previous evaluations, that the supervisor has.

I would concentrate on the progress evaluation, because that has to be done, and has already been deferred once.

As far as the travel is concerned, make sure the supervisor, or at least the secretary, understands that you need some notice, and will assume you are not traveling next month unless there is a definite decision that you are traveling.