Hi guys,
I work for CItigroup (I'm really NOT proud of it). Maybe I can help.....
CitiCards use the Exchange Quay address, CitiFinancial & Future Mortgages go to 6 Admiral Way, Doxfor Park, Sunderland, Tyne & Wear SR3 3XW and for CitiBank it's 25-33 Canada Square London (Canary Wharf). I'll use the internal address book to find you names and numbers if you let me know who you're after.
http://www.innercitypress.org/citi
D