One point that no-one has mentioned so far - what would the point of spreadbetting be if the profits were to be taxed?
Anyone who is making sizeable amounts, that is enough for the taxman to take some interest, would presumably be trading in sufficient size to warrant going fully to direct access if they were now to be taxed on their profits. With the tax advantage removed, why would anyone pay more in spreadbet costs when trading through direct access would cost far less?
Leading on from this, would the taxes paid by these traders on the profits from direct access offset the decrease in the amount of tax that the spreadbet firm pays because it no longer has the business of these traders?