This is fine if you're an island thousands of miles from other large population centers. The problem with Europe is that you're never more than a few hours drive from the next country. So even if every carrier in the UK agreed to block stolen phones, I can be in France within 120 minutes of leaving my house and I can sell them there.
This would need to be Europe wide to have any effect here.
Actually there is an world wide database (http://www.gsmworld.com/our-work/programmes-and-initiatives/fraud-and-security/imei_database.htm) with an blacklist. But as long as there are carriers in neighbourging countries, who would rather sell airtime than block their customers, its is not going to be effective.