Why was our garlic butter made in France, much nicer than garlic butter in England?
The UK supermarkets have the opinion that British people like milder garlic, so most of the garlic you find in the UK supermarkets, even organic garlics, are of a very mild variety. Also, they are bred for yield, in softer soils, so they produce bigger bulbs but less strong. 

Garlic found in most French and Italian stores is much stronger, as that is what people demand. It is usually hardneck, rather than softneck garlic, and hardnecks tend to be much stronger. French garlic is usually grown in stronger soils, so it produces a stronger flavor. 

My solution is to grow my own, 3 bulbs planted usually yields a years' worth of garlic for me, and because I have clay soil it has a strong flavor. It's by far the easiest and most rewarding thing I've ever grown. 

If that's not your cup of tea then ask a greengrocer to stock a stronger variety of garlic, or order it from an Isle of Wight supplier. Of course, you could just use about 4 times as much to get more flavor.