The surname Ireley doesn't exist in Great Britain as shown at
http://kevdb.infospace.com/_1_DLPUR802KUPVHZ__intldb/wp/intl/results/kevdb?OTMPL=%2Fwp%2Fresults.htm&QFM=N&QK=5&KCFG=UK&QN=ireley&QF=&QC=. Neither is it a placename there as you can see at
http://en.wikipedia.org/wiki/List_of_United_Kingdom_locations:_I#Ir. Moreover, I've been unable to find any record of any immigrant to North America bearing that name, which means that it's most probably an alteration of something else. The evidence I've been able to gather suggests that it's an alteration of German Ehrle or Oehrle, much like the American name Early as you will find at
http://www.ancestry.com/trees/awt/main.aspx. Another fact that points to a German origin is that the daughter of the first recorded Ireley married someone named Christian Eckenroth who was obviously of German extraction as you can see at
http://awt.ancestry.com/cgi-bin/igm.cgi?op=GET&db=kjh&id=I06813