I'm in the process of buying my ex partner out of our joint home. Would I have to inform my mortgage lender that I intend to rent the property out... by law ?
Your current mortgage facility almost certainly has a condition written into it that you can't 'buy to let' without the permission of the lender. If you fail to inform the lender that you've rented the house out you'll almost certainly be contravening the provisions of the Fraud Act 2006 (in respect of 'fraud by omission'). The maximum penalty is 10 years imprisonment.