Much as you'd hoped it had gone away, it has been dragged up again and it will take you some time to deal with that fact.
Although the police are apparently building a case it doesn't necessarily mean that you will be required as a witness but, even if you are asked to give evidence, you're not obliged to agree.
A significant number of paedophiles plead guilty in the hope of a reduced sentence because they know that they are even more despised in prison than they are in wider society. When this happens, some victims feel cheated of their day in Court, their opportunity to speak out against those who are responsible for causing them such horrendous pain and emotional distress.
Only you can decide whether you are willing to talk to the police but, for me, the acid test would rest on the probability of my evidence preventing another child suffering at the hands of the perpetrator.
You are between the proverbial rock and a hard place and I wish I didn't have to ask this question, but if your lack of co-operation with the police meant that your abuser went free to sexually molest more children, would you rest easy in your bed?
It takes courage and bravery for a victim of sexual abuse to revisit the past; the fact that you have managed to overcome your childhood experiences, albeit that they cannot be completely erased from your memory, suggests that you have these two qualities in spades.
Whatever you decide to do, I sincerely wish you well for the future.