Hi - I know you said you want someone to do this on-site, but I'm confident I can complete your proofing from my desk in the states and email/Skype with you with questions or feedback (either way). I'd make myself available during your office hours, of course.
I am an experienced writer, editor, proofreader and copy editor, and would be more than happy to complete this project for you.
You didn't mention how many pages are involved, so I left the delivery at the default 3 days, but to be honest, it should only take me a day. Unless you would like me to make suggestions that are outside of the spec'd spelling/grammar (my ex-husband was English and in advertising, so I spent a dozen years living the whole UK vs UK way of communicating :)
I'm more than happy to do a couple of pages free, as proof of ability. (The milestone calculator insists I have a minimum of 5 in there but you can ignore that.)
Warm regards,
Cindi
cindis . smith @ gmail . com