100% The first past the post system definitely needs to be abolished. It's the primary reason the Tories were allowed to desolate our country, but that's a debate I've seen fail to come to fruition at least twice in my lifetime.
Creating this party addresses the more immediate threat of labour collapsing, with no real alternative for socialist minded voters. Some may choose to vote for green, but a lot would have likely abstained rather than continuing to vote these clowns in. This, provides an alternative, which if enough people sign on for, could provide the catalyst for change.
Once the ruling government is focused on social reform, then maybe we have a chance on sorting out the gerrymandered mess that is UK politics. But until then, I don't see Kiers lot even entertaining the notion, let alone changing the system.