Do they stop your money entirely in migrating from ESA to UC?

Newcad

How it works is that when you migtate to UC your IR-ESA (and your Housing Benefit if you claim that) are paid for another two weeks after you claim UC - and you don't have to pay it back.

So in effect you get paid double those benefits for two weeks.

Then as said if you need to (or just want to), you can also get a UC Advance which you pay back at so much a month from your UC until it's been paid back.

PS. When I migrated I took an advance of just the standard UC allowance, I didn't  really need it but it was an easy interest free loan to buy some things to make life easier/better (Some new clothes, a new microwave, an air fryer, etc.) whatever you want/need the chance of an interest free loan with no questions asked is there when you migrate to UC.