The government has made money available for improvements to high street shopping centres, Wiltshire Council are charged with administering this, however at the moment they appear to favour Salisbury, Chippenham and Trowbridge.
Westbury TC need to put forward plans to upgrade the High St, they should be ambitious, and in my view they should start with the removal of the rotunda and look at ways to join up the High St, with Edward St, and Marristow St.
As has been said it is unlikely that a private developer would be prepared to invest, and the council need to find out what the people and businesses of Westbury want.
The Neighbourhood plan gives the council the opportunity to discuss this issue and to find out what the people want and to tell them what is possible to achieve, but they also need to seek expert and informed opinion.