british folks

hey i'm thinking about maybe going to the leeds area from the u.s.. possibly sometime this summer. i've heard it's really hard to gain citizenship, work visa's etc. i currently live close to transient status, i can live comfortably at pretty hazy conditions. so what i'm asking is, how hard is it really to gain proper authoritive permission to reside there? or how possible would it be to work there under the table? has any of you been through this type of situation with friends/family?