Hi wal1963
Welcome to the forum.
You might want to have a look at the following FAQ which explains where everything is;
www.benefitsandwork.co.uk/guides-for-claimants/faq/forum.
When you apply for UC your claim for HB will cease.
Depending on your circumstances you may get a 2 week run on. We would advise you to seek advice from your local Welfare Rights Organisation;
advicelocal.uk where they will be able to take all your circumstances into consideration when giving you advice.
Gary