Your IP has the restriction on the property, as you undoubtedly have a fourth year equity release provision. These are placed on the property records at H M Land Registry, to avoid people selling their properties without notifying the Supervisor.
As your IP has already agreed to the sale, it would have been silly not to, they should not be dithering about withdrawing the restriction. I suggest you get your solicitor to exert some pressure to get this moving. Sounds like it may be lost in someone's in-tray, and you don't want to lose your purchaser.
Let us know how you get on.
Regards, Melanie Giles, Insolvency Practitioner for over 20 years.
View my IVA blog at:
http://melaniegiles.blogs.iva.co.uk