There are other factors there too but I think UK military aid made a significant difference in increasing the chances of Ukraine holding off the Russian invasion and people have a short memory of say the German and French positions early on, Germany even blocked Estonia from sending old soviet artillery that had been sold to them from former East German stocks.
Similar thing with the covid vaccine response and not relying on inefficient EU bureaucrats there, people could say ackchually the UK could have gone it alone on that anyway but back in reality even while on the way out of the EU there was an outcry here at the time when the news broke that the UK would not be joining the EU's vaccine program and had the UK still been in the EU it's rather less that a UK PM would have taken that decision.
Similar issue with this case, you'd have more pressure to stay aligned with France and Germany whereas with a greater degree of independence, the UK can be more nimble in how it responds. Certainly not the only factor though, look at say Corbyn's recent interviews - he dodges the question on whether he would have even authorised the sending of arms with some deflection about how Biden won't provide fighter jets etc.. would be very easy for someone like him to have simply taken the French & German position and stated he was going to try and have a conversation with Putin and how he opposes the invasion but believes peace is the answer... and lots of people would have sucked it up thinking he was a very sensible PM and being thankful that clown Boris wasn't in power as he'd have started WW3 by now etc.