You should immediately have a Restriction (previously called a Charge) entered on the property Registration at the Land Registry. This prevents the property from being disposed of by anybody and in any way at all until your claim is settled (you do have a substantial claim). It is not a DIY matter but requires a solicitor to ensure that the wording of the application is acceptable to the LR Registrar. Cost plus or minus �200. Don't delay, if the application is accepted you will be secure in about a week.