Please know that I have just googled this list of companies as a reference and have not checked whether these companies are legitimate.
UK Companies
Actor Showreels UK
Professional Award Winning Actor Showreels – Slick Showreels
Killer showreels
Mandrake Media
Role Film
Self Tape UK
Showreel Editing

Los Angeles
http://www.lareels.com/
Jig Reel Studios