Hi Martinlee
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.
You have to get your timing right, as soon as you get your ESA payment apply for UC.
There is usually a 5 week wait from completing UC and your first payment.
your assessment period is between two periods, for instance 11 July and 10 August, you will then receive your UC allowance 7 days later (17th of August) hence 5 weeks.
Gary
