DH and myself both had a significant relationship before meeting which we disclosed to SW. Insignificant relationships we ignored (1st boyfriend, 1yr casual dating etc). Neither of us had had contact with our exs since breaking up 15years ago and were nervous of them being contacted.
However, we were assured that our exs would be asked a simple question along the lines of 'is there any reason why xxx should not be considered to adopt?. Not so intrusive and if they are decent they will simply reply 'no'.
It helped us in that the interviewing SW said she had adopted and her ex was not very nice when asked the question; but LA took it with a pinch of salt and looked at all the evidence rather than just the word of a bitter man.
We were also told that it was something they had to do because an adoptive dad had had an abusive relationship in the past, the ex was not interviewed and the adopted child was hurt (can't remember details) in some way because of this. The child might not have been placed with the adoptive parents if the abusive past had been known.
We took a deep breathe and just hoped nothing would come of it, and from what I understand (but don't know because LA can't tell you what was said) both exs said 'nothing to worry about.'
We are now provisionally matched with a mini and all being well, he'll be with us inside of a month!
Best thing to be is honest. Fingers all crossed for you.