 Vandetanib and 131I-mIBG will be given in 12-weekly cycles: 131I-miBG will be given on day 1 of each cycle and vandetanib will started on day 1 of each cycle and continue to be taken once every day. The phase I trial aims to determine with recommended phase II dose of vandetanib either 100, 200 or 300 mg once daily - the dose of vandetanib that patients will receive will depend on the dose under investigation at the time of patient registration. 