> The Govt has ... decided to commission a new generation of new nuclear power stations

No. We have a privatised electricity generation industry now, not a nationalised one. In some way the government will encourage it, but it is for private industry to decide if nuclear generation is economic in light of the tax/incentive regime.

So far the private liberalised generation industry worldwide has not built a single running nuclear power station, because they have not been economic/risk wise better than the alternatives. All running nuclear power stations were built by state-owned or regulated utility monopolies, where future cost risks were borne by consumers rather than suppliers.

We'll have to look at the details of tomorrows announcement to see what the incentives are.

The first European Pressurized Reactor being built in Finland is at least two years behind schedule and more than 25% over budget. EDF (majority French state-owned) is hoping to build these in the UK, but the economics must now be extremely flakey even for a company trying to support a state nuclear industry. Just looking at the economics now, super-critical coal-fired power plants (which have higher thermal efficiency than traditional coal plant) are looking the better economic choice - but are obviously not great for carbon emissions.

Even the UK nuclear industry's own magazine is no longer sounding that confident, and reports tha EDF has been calling for wholesale price guarantees or carbon-pricing:

Investors such as ourselves are prepared to invest in nuclear without government subsidy,” but called for a long-term guarantee on a minimum carbon price, which, the company claimed, “is not a subsidy for nuclear.”

The same is true in the USA, where more government support is available to new nuclear projects. Even with the incentives in the US Energy Policy Act, it seems unlikely that new nuclear plants will be ordered without a price on carbon emissions. As Lew Hay put it: “Based on our analysis, nuclear power will not be economic without a sustainable carbon price of roughly $30 per ton, or more.”

We'll have to see if tomorrow gives the industry enough incentive/subsidy so they build something.

> At least 20% of our future energy will be sourced by nuclear energy.

No. Electricity generation is not all of "our future energy", in fact a minority. 20% of electricity generation is I recall about 4% of our total energy use. Even if we go wildly nuclear that doesn't solve the energy problem. We have to think more widely, about transport and space heating for example. Greatly improving house-insulation and encouraging micro-CHP would probably save more gas than 20% nuclear electricity would.