Would they agree to a charge being put on?
In which case you can get a charge deed drawn up (CH1 form from Land Registry) and have it lodged at the Land Registry with an AP1 form (to change the title register) for a �40 fee.
If there is to be a restriction to prevent sale without your consent (though if repossessed it can be overriden so check there is sufficient equity) it will also need to be sent with a Form RX1 or AN1. The consent is implied if son and daughter sign the charge deed.
I'd get a solicitor to draw up the charge for you, I do them a lot and only charge �100.00 plus VAT and disbursements such as getting title details normally as not a lengthy process.
It means you are more protected. Son and girlfriend should be offered independant legal advice.
If they would not agree to sign a charge then you can put a Unilateral Notice on, Form UN1 which needs to be sworn as a statutory declaration (criminal officence to swear a false one) and sent with �40.00 fee.
You could attach the agreement you had signed and any other correspondence.
All the forms are here...
http://www.landregistry.gov.uk/www/wps/portal/ !ut/p/c1/04_SB8K8xLLM9MSSzPy8xBz9CP0os3gfN1MTQ wt381DL0BBTAyNjY0cTE19PQwN3M6B8JB55A2J0G-AAjoR 0-3nk56bqF-SGRpQ7KioCALdDEtQ!/dl2/d1/L2dJQSEvU Ut3QS9ZQnB3LzZfTEY1NDE4RzdVOVVUNTAyMzNBNDRNSTE wRzU!
Ring the Land Registry and see what they suggest. You can find the right one (for where the property is) here...
12:59 Wed 11th Jun 2008