Emission exports
"The government bureaucrats don't realise that broadband communications mean it's just as feasible to operate your lights-out data centre in Dubai, Brazil, India or Malaysia as it is to operate it in London's Docklands."
Some truth on that, but no amount of broadband will do anything about the speed of light. The latency to some of those locations will be in the 100-200ms region for a round-trip. That makes it unsuitable for quite a lot of IT uses, especially as complexity increases. For some applications, like real-time trading, every millisecond counts.
There are also issue about security of data, and European data protection standards will prohibit, or at least make very difficult, the export of some types of data to these locations.
However, the biggest issue with any carbon tax is that is can simply export the CO2 emissions to a different country (as has happened with the CO2 emissions associated with manufacturing industry). A tonne of CO2 is a tonne of CO2, whether it is emitted in China or Cheltenham. Of course if the activity is exported to a country with low-emission electricity generation (effectively that's cheap hydro or geo-thermal), then that will save emissions, but that will only happen if the pricing mechanism across the world is common.
In other words, a CO2 tax in Europe alone would have only limited effects as any industries which are inescapably CO2 intensive will migrate to cheaper climes where this is possible.
Of course we could build some more nuclear power stations, although for some bizarre reason, these were not properly recognised as low-carbon generation systems.