Yes it will impact future E&P.
If you are a corporate and have a choice between investing in a country that has a stable and long term corporation tax policy, or one that has a policy that changes at random depending on a number of political factors then you will invest in the first not the second, especially if you are going to invest for decades in infrastructure.
The North Sea is not looked on as a great place to invest in E&P. There are many more lucrative areas around the world. So a poor tax environment is not going to help that at all.
If you want to cite BP as a particular example, yes it has profited from North Sea operations because of Russia. But it has also had to write down a lot of investments that it had in Russia, so as a business it is swings and roundabouts. It also isn't that big a producer (maybe 4th or 5th largest) in the North Sea.
Most people seem to have forgotten there is already been a windfall tax in place by the UK on North Sea profits.
As for the EU efforts, a significant proportion of the EU energy sector is public owned. So it's probably just a smoke and mirrors exercise.
Generally I'm supportive of taxing companies who wriggle out of paying enough tax - there are several large ones that do this. But taxing energy companies when we actually need more not less investment in energy (oil and gas as well as renewables) seems like madness to me, and probably is going to be long term counterproductive to energy security.