If by Best UK umbrella company you mean you are looking for a better take home pay due to better tax efficiency then you are in the right place!
Many contractors want to earn more money at the end of the day, and there are so many umbrella company services that choosing the right one can be difficult..
If you just want a ordinary umbrella company to simplify your billing then go for any of the ones found on google. If however you are seeking an umbrella service that can deliver a better ROI than that, you may want to click the link I put above here and check out contractor tax solutions services..
other than that I cant really reccomend much more as its a bunfight all these umbrellas fighting for the best position and charging fees for admin even when you arent contracting.