I've heard the best way to hear one is to mimic the sound of one, if there is one near by it'll soon come to see who the intruder is. Don't know how true that is as my ability to mimic a cuckoo call is sorely lacking.
I hear it every day, many times, here in Hove. I thought it was wonderful yet unbelievable when I first heard it last week. It quickly dawned on me that one of the little boys next door has a cuckoo whistle which he spends most of the day blowing. But the very first time he did it he got me:-)