To my knowledge the standard length of time is 3 months in arrears before any action is taken.
I found this information:
The lender must stay within repossession laws if they are trying to repossess your house. Your house cannot be repossessed unless the lender has been given permission to do so by the court. No matter how imminent repossession may be, it can be stopped at any stage in the process. Repossessions don’t happen automatically and even if a mortgage lender is threatening legal action against you they would usually rather you clear your debt with them than have to take you to court for it.
If you are in payment arrears, stay in contact with your lender and pay what you can.
In this current climate where many are unable to meet mortgage payments then lenders need to be more reasonable and flexible working with the home owner for a satisfactory solution.
http://www.medhead.com