They will write to the mortgage company. Ours even did a drive by valuation to check what the house was worth and charged us for the privilege!
I believe Andy mentioned earlier that you need to tell your IP if you take a payment break as it affects your disposable income for that month and may affect the equity in the house.
Sharing from experiences of dealing with debt
The greatness of a man is not in how much wealth he acquires, but in his integrity and his ability to affect those around him positively.
Bob Marley. http://kallis3.blogs.iva.co.uk