Reads like propaganda. If it's true that nuclear is just too expensive (and how would I know?), then all he needs to do is to advocate that operators post bonds (or pay pretend interest on a state-funded equivalent) for decommissioning costs.
And on your second point, fine: let's make operators post bonds, and watch as they scramble not to build new nuclear plants even faster than before.
The general run of things in the UK as I understand it seems to be:
0. Many billions are invested in public nuclear R&D. Electricity market is then privatised.
1. Nobody builds new nuclear (and nobody wants it on their doorstep either, especially in a country this small).
2. Government skews market in favour of nuclear by taking on liabilities for decommissioning (and de facto also disasters, which although rare are catastrophically expensive).
3. Operators/investors still aren't sure they can make a profit.
4. Government skews market further by offering a floor price for nuclear-generated electricity (additional public subsidy).
5. Operators/investors are still somewhat uncomfortable regarding risks and public opinion, so government gets into protracted negotiations to give them whatever the hell they want.
So nuclear here is essentially being subsidised three ways, and is still struggling to secure an investor.