Note two things about this statement:
1) Nothing you say will be used for you.
2) Everything you say will be used against you.
I forget the lawyer's name, but the above is paraphrased from a former prosecutor turned D.A. Never put forward any statement to the police without at least consulting your lawyer first. Even if you're innocent, even if you're providing a witness statement. Anything.
By all means - give witness statements. Help the police do their job. Just be sure to speak with a lawyer first. There's a very high chance that even though you did nothing wrong you'll incriminate yourself by speaking up.