Not quite correct. Boris Johnson flew to Ukraine and told Zelensky, "Putin should be pressured, not negotiated with" and further said that the west (UK and US) would not provide the security guarantees for Ukraine as in the peace plan. So it was not that Ukraine "had backing from the US and UK" it was that the US and UK wanted war and not peace, and that has not changed.
There are no good guys in this war, except for the conscripts and Ukrainian civilians. Since the US-backed coup in 2014, Ukraine has become a US vassal state, ramping up for war against Russia. Not good. The US will not accept that any other country has a sphere of influence. Not good. Obviously Russia invading is not good. But here we are.
The only way out now is through WWIII and most likely the end of the world, or Ukraine trading land for peace and accepting neutrality. The only real questions is if we all die, or if not all of us how many more Ukrainians, Russians and - of course they are there - western "advisors" will die before there is a negotiated peace.