The Highway Code is a little unclear and implies your can't even use it as a sat nav.
Mobile phones and in-vehicle technology
Rule 149
You MUST exercise proper control of your vehicle at all times. You MUST NOT use a hand-held mobile phone, or similar device, capable of interactive communication (such as a tablet) for any purpose when driving or when supervising a learner driver. This ban covers all use of a hand-held interactive communication device and it applies even when the interactive communication capability is turned off or unavailable. You MUST NOT pick up the phone or similar device while driving to dial a number and then put it in the cradle for the duration of the conversation. You MUST NOT pick up and use your hand-held phone or similar device while stationary in traffic.
There is an exception to call 999 or 112 in a genuine emergency when it is unsafe or impractical to stop. There is also an exception if you are using a hand-held mobile phone or similar device to make a contactless payment at a contactless payment terminal. Your vehicle MUST be stationary, and the goods or services MUST be received at the same time as, or after, the contactless payment.
Never use a hand-held microphone when driving. Using hands-free equipment is also likely to distract your attention from the road. It is far safer not to use any telephone or similar device while you are driving or riding - find a safe place to stop first or use the voicemail facility and listen to messages later.
You may park your vehicle using a handheld remote control app or device. The app or device MUST be legal, and you should not put other people in danger when you use it.
Rule 150
There is a danger of driver distraction being caused by in-vehicle systems such as satellite navigation systems, congestion warning systems, PCs, multi-media, etc. You MUST exercise proper control of your vehicle at all times. Do not rely on driver assistance systems such as motorway assist, lane departure warnings, or remote control parking. They are available to assist but you should not reduce your concentration levels. Do not be distracted by maps or screen-based information (such as navigation or vehicle management systems) while driving or riding. If necessary find a safe place to stop.
As the driver, you are still responsible for the vehicle if you use a driver assistance system (like motorway assist). This is also the case if you use a hand-held remote control parking app or device. You MUST have full control over these systems at all times.
The actual legislation states.
Breach of requirements as to control of vehicle, mobile telephones etc.
A person who contravenes or fails to comply with a construction and use requirement—
(a)as to not driving a motor vehicle in a position which does not give proper control or a full view of the road and traffic ahead, or not causing or permitting the driving of a motor vehicle by another person in such a position, or
(b)as to not driving or supervising the driving of a motor vehicle while using a hand-held mobile telephone or other hand-held interactive communication device, or not causing or permitting the driving of a motor vehicle by another person using such a telephone or other device,
is guilty of an offence.]