I'm from Texas and I've lived in London for 15 years. Hands down, this is the best butcher in London.... The best quality steaks and lamb I've had outside of Texas - and they're friendly as hell.
This is not a 'meat under glass' residential butcher - they are probably the place that supplies those butchers.
Their hours are funky, but if you can make the trek it's 100% worth it.
Even if they were more expensive I'd still go here, but the reality is you'll pay less and get freshly butchered meat to order that tastes better than anything you've ever had before.