With the Council Tax, ring ahead with the date that you leave your current house and move into the new one, that way there will be no overlap and no risk you could end up paying for your old house - they do refund it but it takes ages.
Echo PB with the wedding suppliers - especially if you will be leaving from your new address. You can do the TV licence online.
Mobile phone operators, opticians, vets, any HP loans that you have i.e. for electrical appliances and so on, and if you have gym memberships.