There is no exceptional circumstance which justifies 'releasing' ( actually destroying) any greenbelt. Reducing the amount taken to 5% is a failure not a triumph. At this point in the history of mankind we have to increase and develop the green infrastructure urgently.
The town centre is struggling for many reasons, not least the development of big out of town shopping areas. So now the town centre should be developed as an excellent place to live, with everything near and much less need for car use. New buillding on green belt land will not help to regenerate the town centre.
There is no reason to suppose people in the proposed new development will use public transport rather than their own cars, contributing further to the road congestion.
The South East extension is unlikely to fulfill local need for housing, rather will encourage a further trend to being a dormitory for the big cities on our doorstep. Not only will mass house building destroy the character of the area but will also erode the sense of community, uniqueness and character of the area. Already we have people who live here but work, shop and socialise in Manchester or Liverpool. I have met people personally, who have lived locally for several years and have no familiarity at all with the town centre.