Can I ask what equity there was in this property when you agreed the division of interests, and on what basis the agreement for such sharing was actually made? As Catallus has already indicated, the agreement looks a little odd, and may well be subject to challenge by a subsequent Trustee in bankruptcy if your husband's IVA is not accepted or subsequently fails.
Is is perhaps that the declarations of solvency was more likely a statement of means, which valued your husband's share at £5,000. If this was drawn up correctly, using the market value of your property, then your flat ought to be safe.
Regards, Melanie Giles, Insolvency Practitioner for over 20 years.
For further details contact me at
http://www.melaniegiles.com and view my IVA blog at:
http://melaniegiles.blogs.iva.co.uk