I think you need to forget about Labour - they are dust at the next election. I think it will be the smaller parties that hold sway - Reform, Greens, Lib Dems, nationalists.
This of course is a main reason why we need electoral reform. It's all well and good clinging to First Past the Post in a system which has two (maybe .5 if you count the Lib Dems and latterly SNP) parties. Then most votes wins makes some sense as you're always going to end up with, at least on a constituency level, the winner being someone who won, at worst, 45+% of the vote (or round about). But now that our politics is fracturing we've got on a GB wide level five competitive parties and in Wales and Scotland potentially six (as always poor NI is the redheaded step-child in this conversation but they have similar issues just with the NI specific parties rather than the GB ones).
It's absurd that Labour in 2024's General Election won 411 seats on just 33.7% of the popular vote (when Tony Blair was winning those sorts of seats in his pomp in 1997 and 2001 he was getting 40+% of the popular vote). It's absurd that UKIP, in 2015, got 12.6% of the vote and one MP and the Lib Dems got 7.9% of the vote and eight MPs whilst the SNP got 4.7% of the vote and were rewarded with 56 MPs. First Past the Post does not function properly in a world in which there are more than two (ish) viable parties.
We are facing a scenario in 2029 in which wave of constituencies are going to be won on basically a coin toss (possibly literally!). I reckon we're going to see constituency after constituency where the result will be something like Labour 20%, Green 19.5%, Lib Dem 18%, Conservative 19%, Reform 21% and Others 2.5% giving Reform a victory on 21% of the vote with 79% of voters opting for other candidates (and in this case 57.5% opting for centerish lefty parties but getting a hard right party). Or vice versa you'll have a seat where it might be more like Labour 10%, Lib Dem 10%, Green 25.5%, Conservative 24%, Reform 24.5% and Others 6% giving the Greens a seat where there was a strong preference for a right wing party.
Obviously quibble about exact percentages but the point isn't to Mystic Meg what the votes will look like but to simply illustrate what I reckon will be a repeated pattern again and again in 2029. Parties are going to win seats on a sliver of the vote in a constituency and that will then feed into another Parliament where the governing party either alone or in coalition can claim via the way our system works near complete power over the functioning of the country even though only a fraction of the population voted for them.
This strikes me as being extremely unhealthy for a country. Having potentially wild swings in governance based on a few percentage points or less (quite apart from the disenfranchisement issues, a constituency voting for largely right wing parties getting a left wing MP or vice versa, safe seats such as they are meaning a vote doesn't count, etc etc). I suspect it's part of the reason we're in the state that we're in to be quite honest.
But, as always, the party that benefited from it last is never willing to take the view of what might be better for the long term national interest. Labour have gone quiet on electoral reform now that they're in power via that system and even Reform have become much less chatty about it as well now that they're doing better in the polls and thinking they could win a serious number of seats under the existing system.