Why on God's earth would you allow any contractor to start work without a finalised cost is beyond me.
It will be more expensive to start again with a new contractor, so I would suggest you bite the bullet and get them to return. Since they haven't done the work correctly ask them to soak up the cost for remedial works which should take about an hour, issue the mwc and go forth.
As for costs, a double socket including back box, socket and cable is about £50 including work and materials. So four would be x4 or about £200. If they argue that sort of figure rate then ask them to qualify and post up here
It will be more expensive to start again with a new contractor, so I would suggest you bite the bullet and get them to return. Since they haven't done the work correctly ask them to soak up the cost for remedial works which should take about an hour, issue the mwc and go forth.
As for costs, a double socket including back box, socket and cable is about £50 including work and materials. So four would be x4 or about £200. If they argue that sort of figure rate then ask them to qualify and post up here