Car Insurance in UK

I am regrettably in the process of moving back to the UK and am trying to formulate a budget for life there now. Getting a car insurance quote is prooving extremely difficult in that the companies contacted so far have all refused to quote because I cannot give a precise address or a british car registration number. All I want is a rough idea of what I can expect to pay based on residence in Bedfordshire with a 2.1Lt diesel Renault Saffrane, over 20 years no claims and either fully comp or Third Party. I can then decide whether to bring my car with me or stop driving altogether. I should add that I am over 70. Can anyone help either with the name of a company who will give me a rough quote on this basis or tell me where I can get the information.