Thankfully, there are options available if you wish to move into a property that you are currently renting out on a buy-to-let mortgage.
Some lenders simply allow you to remortgage your existing buy-to-let mortgage onto a residential one (providing you meet affordability and criteria requirements) and there may be costs involved such as early repayment charges. However, this is not the case for all mortgage lenders as some do not offer residential products or allow this type of remortgage to happen.
Some lenders simply allow you to sign a form or letter to confirm you will be moving into the property on an owner occupier basis, on the agreement you will move to a residential mortgage upon your current rate coming to an end.
In any event, you should contact an independent mortgage broker and your lender prior to moving into a property with a buy-to-let mortgage.