Just an update to this one. The leak was on the main line that supplies mine and two other cottages. The main just happens to run under my back garden. The leak is chargeable nonetheless, but Dee Valley Water run a subsidised repair scheme that means they pay the first £220 towards the cost of repair. Thankfully his quote came in at £189 so I won't have to pay anything. Also if it goes again the cost will be shared by the two other properties.
Thanks to all who posted.
Thanks to all who posted.