Fraud prevention

I’d like to get a feel for what people are doing about fraud prevention.

I work for a company which processes 100-250 online orders per day.
We use a bespoke cart system which integrates with Datacash for card processing. Datacash will validate the card details and check the address details of the card, and, let us know whether this matches the cardholder address.
After that it’s down to us.

We’ve developed the policy of investigating any orders where the billing/delivery/card address differ, or where the bank do not confirm the address, or which have a high order value. We manually use online services (phone records, electoral roll etc, company records) to see whether the customer lives where they say. But a lot of the time this process proves inconclusive and we have to wing it. Also the process is quite time consuming and definitely results in refunding many genuine orders.

I’m about to implement 3d secure on my card payments, but I wondered what other options were available and cost effective. Does the cost of refunding possibly genuine orders outweigh the risk of chargebacks? We’re in the UK, by the way.