From The Guardian article which Dave the Gnome linked to:

"But it is understood that in an analysis by the storm overflows taskforce, made up of the Environment Agency, the water industry and Ofwat, which is yet to be published, much more modest costings have been estimated for tackling the scourge of raw sewage discharges.

Sources say the figure of £660bn appears nowhere in the report. The Angling Trust said the report cites a range of lower-cost options for progressively dealing with the worst and most damaging sewage discharges ranging from £3.9bn to £62.7bn, with an impact on average water bills of between £19 and £58 a year.

It is also understood to estimate that an overall plan to reduce spills from storm overflows to an average of 10 a year in sensitive areas would cost between £13.5bn and £21.7bn."

But it is understood..
Sources say..
It is also understood..

We will have to wait and see what is in the storm overflows taskforce analysis but there does seem to be a huge difference of opinion on the costs involved.

The government have said they will look at this again. U turn around the u bend? We shall have to wait and see if they follow through on that promise.