Maybe for swing trading.
For daytrading, the UK brokers are unusable in my opinion.
Gigantic spreads compared to the underlying (IB and colmex have the same tiny spreads as the underlying), and the platforms are a world apart from a direct access trading platform (which is what the colmex platform has copied) in terms of speed.
Every person has diffrent methods to jugde and review the best broker. I personally use IG Index and Capital Spreads for my spread bets and I am happy with them, and yes you're right, they are good for swing trading purposes