Ideally we should do both.
But.
As you say, the optics of the whole thing don't sit right with the everyday man and woman. No signs of help for the population in the UK, only paper talk and leaks, whilst the government are heavily publicising the aid they are sending to the Ukraine.
If there is only so much money to go round it should be spent here before the Ukraine. Johnson is more than likely lying, he's good at it.
Just because we could stop helping them doesn't mean the rest of the world (mainly Europe) would, supply would still be low and demand would still be high, the problem wouldn't go away. Even if the fighting stopped (through a putin "win" or a loss) it would be unlikely he would go to normal service anytime soon.
Same as if every country stopped helping Ukraine, Putin couldn't take Ukraine when they had little help, and fresh soldiers, he's got no chance even if they still got half the help. High might end up satisfying himself by holding west Ukraine, but it would only be a matter of time before he went after the rest and it all starts again. Or Ukraine try and take it back, which they would be entitled to, and then what if Putin stops the gas again, do WWE attack Ukraine? Of course not.
After he's done with Ukraine he could just do it again with somewhere else, he's hardly likely to play nice for the next 10 years, and then the problem starts again, and then again, and then again.
He needs to know that it won't be tolerated, and if he cuts supply, then fine, the developed nations in the EU/ Europe are more than capable enough of dealing with that, if they actually chose to.
All the time over the next decade or two there should be nobody whinging about any sort of renewable energy supply/ construction, put in place on our own shores, which we can have full control over. They solve problems like this, and also massively help with the green issues. Even if people aren't even remotely green, they surely can't fail to see that it's going to be better for their pockets in the long run.
It's either spend £100m or £10bn now (or whatever it is) to try and solve the problem (and make Russia give in), or spend 5x that over the next decade or whatever. Whilst the world is moving against fossil fuels, Putin knows their days are numbered (personally, and with regards to Russia having a grip on fossil fuels), and he is going to use what control he has left to grab as much land and resources as he can get his hands on.
There is only so much money to go around, the problem is the top 10% have 50% of it in the UK.
Taking a £100m loan to avoid paying a billion to a lunatic over the next decade is money well spent.
