Hi Nicola
Nails UK is now known as just 'Nails'. Nails is an excellent trade mag covering basically the same as Professional Nails but with extra content. If you become a member of ANT you get your subscription with Nails free!
Scratch is more of an upbeat, funkey style mag. Prof Nails is going it alone later in the year, so I guess the mag will be more in direct competition with the other 3.
I personally subscribe to all 3, although my Prof Nails runs out in Sept. Thinking about it, I think I will continue with all 3 for another year to find out which one, if not all of them, I prefer!!
Sorry, don't know if that helped or not,
Adele