The meterbox is the property of the end user and is responsible for its maintenance. You say its a surface mounted box, as long as the backplate is ok - just buy new box and replace cover- 4 push in plastic jobbies.
The meter box will normally be maintained by Transco, United Utilities etc , I have informed many customers to contact their supplier, they have raised the job for the gas transporter and they've had their's repaired or replaced free of charge - no hassle.
'The meter needs to be protected from the weather and vandalism'
'How can you protect from vandalism???'
The meter box protects the meter and components, from weather and vandalism !!