Obviously FPTP is a terrible voting system. We've seen that it's prone to gerrymandering, it tends to a bipartisan system, and it gives immense power to a small number of voters whilst effectively disenfranchising swathes of the population. It takes something cataclysmic to produce real change (case and point - the Scottish referendum in 2014 and subsequent election in 2015) and even then produces wild swings. Clearly the SNP's phenomenal success in 2015 was ridiculous, but not really any more so than the dominance of Labour that preceded it. It took a constitutional referendum to produce that swing and eliminate Labour's safe seats, and even then many of the seats will settle down into safe seats (be it for Labour, SNP, Conservative, Lib Dem).
FPTP marginalises voters in safe seats and results in minimal campaigning. It tends to produce majority governments that lack the support of the majority of the electorate. In swing seats, tactical voting is necessary.
Proponents of FPTP talk about strong and stable government. In reality, it produces a bipolar government that swings dramatically from right to left and back again at the whim of a relatively small number of voters.
We need to change the system.
My preferred method is the STV. By ranking candidates in order, you can express a true opinion of your favourite to least favourite candidates. ("Vote 'til you Boak" as they say in Scotland). You don't have to worry about how others vote; if you vote for a minor party and they are eliminated, your second preference comes into play. Lots of the minor parties will actually benefit because they'll attract voters that wouldn't have voted for them under FPTP, and you could see quite different results. Rather than Labour and Tories, perhaps it turns out that the Llama Appreciation Party actually has broad support of the electorate and deserves a seat. And maybe their voice should be heard. By having multiple MPs, you have multiple people to approach. If one MP is a deadweight, you can approach another. If they aren't helpful/don't agree with you, you can find a member who will be helpful. If one MP is elected/appointed to a position such as Speaker, PM, Chancellor or any other major role that significantly takes time away from their constituency work, then they can absolutely take on that role knowing that their constituents have not been abandoned (how on earth John Bercow gets elected despite being completely unable to represent his constituents is beyond me).
STV would see the UK split into larger constituencies that elect a larger number of MPs. This is relatively easy for densely populated areas (the seven Glasgow seats could easily be merged into a Glasgow constituency, for example, that would elect seven MPs). Even relatively rural areas could manage - North Wales could be split into two or three larger constituencies without a huge fuss I reckon. Only the most rural areas would truly have the issue of local representation - the Far North of Scotland and Mid Wales come to mind here. But it's still perfectly possible to ensure that local voices remain heard - there are still the same number of MPs per head of the population, and you could easily pass a law mandating that regular surgeries etc be held across the enlarged constituencies.
The big issue for me with STV is by-elections. Where only one member resigns/dies/is removed from their seat, the election to replace them becomes an AV election. And herein lies a problem. Take a hypothetical constituency where Party A has three members, B has two and C has just one. If the member from party C dies, the by-election will invariably elect a member from Party A making the system less proportional. This did happen - in one of my Scottish Council constituencies we had a lot of by-elections due to the sad death of councillors - but the number of Labour members trebled in spite of a surge in SNP support because Labour remained the largest party. But by encouraging members to nominate a secondary in the event of vacating their seat (which could include a party list of secondaries to be agreed prior to the election), then the effect is somewhat mitigated. You do have the problem with a party list, but so does AMS.
I do like the AMS for Holyrood and Cardiff Bay - it solves the problem wherein a larger number of representatives is needed. That is not a problem Westminster has, so I'm not hugely enthusiastic about expanding the system to there. You still need to enlarge constituencies to achieve the aim, and they can still be gerrymandered at least on a constituency level. It also gives you a number of members without constituencies, potentially creating a "two-tier" system.
AV was not a sufficient change, but I despair that a significant number of people voted against the change because they'd rather have proper PR. This sent a message to the politicians that we are happy with the current system, and I think was a huge mistake. AV has lots of the problems that FPTP has, but is superior in that votes aren't wasted. So sadly, I have little hope that electoral reform will be on the table again within the foreseeable future.