The two main companies are Sporting Index and Spreadex, best to have a look around on their websites.

Basically you have a buy and sell price, the difference being the spread. You can lose or win a fair amount so be careful, today I bought at 35 and if I had got nilled then my liability would have been 35 times my stake.

Conversely the bet made up at 65 so I won 30 times my stake.

You can close out at anytime if you take the price offered, you could trade on the spreads long before the exchanges were invented.

Your first 30 days for just £1