The consideration for such a disposal as is mentioned in section 156A(4) shall be such amount as may be agreed between the parties, or determined by the district valuer, as being the amount which is to be taken to be the value of the dwelling-house at the time when the offer is made (as determined in accordance with regulations under that section).
That value shall be taken to be the price which, at that time, the interest to be reconveyed , conveyed, surrendered or assigned would realise if sold on the open market by a willing vendor, on the assumption that any liability under—
would be discharged by the vendor.
If the the offer is accepted in accordance with regulations under section 156A, no payment shall be required in pursuance of any such covenant as is mentioned in subsection (2), but the consideration shall be reduced , subject to subsection (4), by such amount (if any) as, on a disposal made at the time the offer was made, being a relevant disposal which is not an exempted disposal, would fall to be paid under that covenant.
Where there is a charge on the dwelling-house having priority over the charge to secure payment of the sum due under the covenant mentioned in subsection (2), the consideration shall not be reduced under subsection (3) below the amount necessary to discharge the outstanding sum secured by the first-mentioned charge at the date of the offer to (as determined in accordance with regulations under section 156A).