http://forum.wordreference.com/showthread.php?t=292455
"If you have any questions..."

http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/learnitv48.shtml
CONDITIONAL
"Oleg from the Ukraine asks:

     Could you please tell me the rule for using should in questions like this: 'Should you have any problems, feel free to contact me.' What does it mean? And how does it differ from: 'If you have any questions, please contact me?'

       These two sentences are very similar in meaning. But 'Should you have...' or 'If you should have...' may be used in preference to 'If you have...' if we want to suggest a slight possibility of something happening or when we are making suggestions or giving advice. Compare:

      'If you have any free time, make sure you visit the old town.' (It's possible, or even likely, that you may have some free time.)

       'If you should have any free time, make sure you visit the old town.' (I don't really expect you will have any free time, but if you do...) 

       'Should you fail this exam, you can always re-take it next year.' (I think it's unlikely, but it's possible you may fail it and if you do...)

       'If you fail this exam, you can always re-take it next year.' (I'm just pointing this out to you. I don't have a strong opinion on the matter one way or the other.)    "

       In the day-to-day communication there´s not much trouble wether using one or other, I think.           PP.