Hi there - some good advice already given by the previous posters, and now for some technical advice:-
1  You can continue to act as a company officer for the duration of the IVA, however banking issues may be difficult so do discuss this with your company bankers to make sure that they will continue to support.
2  Your girlfriend will need to be advised of the IVA, as you will most likely be asked to raise equity at the end of the IVA which your girlfriend will have to agree to.  Has the money you have borrowed all be spent on you, or has your girlfriend in any way benefitted from the borrowings?
3  It is unlikely that you will lose your flat, but as I mention above equity raising is a distinct possibility.
4  There are alternatives to an IVA - you could enter into a Debt Management Programme, however this would be open-ended with no interest moratorium or legal protection from creditor actions.  Bankruptcy is also an option, but one I guess you want to avoid given your directorship and flat ownership.
At this stage I suggest that you take more definitive advice from an insolvency practitioner directly.
Regards, Melanie Giles, Insolvency Practitioner for over 20 years.
To have me propose an IVA for you, please visit:
http://www.melaniegiles.com/ivaEnquiry.asp
See customer feedback at:
http://www.iva.com/iva_companies/IVA_Advice_Bureau.asp