There are two tolls operated under concession with the Government – the Severn Crossing and the M6 Toll, with maximum concession lengths of 30 and 50 years respectively. There are a further four local authority tolled crossings, and a number of smaller privately owned tolled crossings. Note that the Dartford crossing has a user charge, not a toll, and similarly the new Mersey Gateway Bridge will also have a user charge.
I do not have information on local authority and privately owned tolls. For the two concessions, removing the tolls would involve changing or terminating those concessions. This would mean a negotiation with the toll operating companies, so costs have not been estimated.