thanks Andrew - the first one was very close. I changed it to
Code:
(?:|^)?[\w]([^.]*wibble[^.]*)($:|\.|\?|\!|$)
to start the capture at the beginning of the sentence ort the beginning of the string, instead of the end of the previous one, and to end on a full stop, exclamation, question mark or just the end of the string
seems right to me. Thank you both for your suggestions.