Going with a spread betting company saves paying tax IF its not your only or main source of income, once the trading starts to overtake any income from another regular job the tax man can argue that you are a professional gambler/trader and therefore tax is payable under income tax.
As far as knowing if your broker/spread better is being honest, its easy enough to have demo's open in other accounts just to see if the price went a long way from the one on your platform.
As far as knowing if your broker/spread better is being honest, its easy enough to have demo's open in other accounts just to see if the price went a long way from the one on your platform.