Short answer
No. A Title Plan is normally used to show the general extent of a registered title. It should not usually be treated as proof of the exact legal boundary line.
What a Title Plan can help with
A Title Plan can help identify the land included in a registered title, compare neighbouring registered titles, and understand the property's position in relation to roads, gardens, accessways and surrounding land.
Official source
GOV.UK explains that title plans show general boundaries and that there is usually no record of exact boundaries.
Official source: https://www.gov.uk/your-property-boundaries
Scotland note
ScotLIS guidance explains that Scottish title plans show the position and boundary of registered properties and are based on the Ordnance Survey map. Scottish property records are handled by Registers of Scotland, not HM Land Registry.
Official source: https://scotlis.ros.gov.uk/help-and-guidance
When you may need more than a Title Plan
If there is a live boundary dispute, a fence has moved, land has been built over, or the exact legal boundary matters, you may need professional legal or surveying advice. A title document can help start the investigation, but it is not a measured boundary survey.
What to order
If you need to understand the general registered extent of a property, order the Title Plan. If you also need ownership, tenure, charges or rights information, order the Title Register as well.
Independent service note
LandRegistries.com is independent and is not HM Land Registry, GOV.UK, Registers of Scotland or any government department.