Our electoral system makes it damned near impossible to elect someone else.
At the 1983 general election, the SDP won 25.4% of the popular vote, giving them 23 seats in parliament. Labour won 27.6% of the popular vote, giving them 209 seats. We are a de-facto two-party state, because the design of our electoral system is drastically biased in favour of the established major parties.
We did consider switching to a fairer electoral system in 2011, but ironically enough we decided against it by referendum.
> We did consider switching to a fairer electoral system in 2011, but ironically enough we decided against it by referendum.
On the other hand, the countries with the most stable democracies (measured in centuries) (US and UK) have two-party systems. So maybe the choice was less obvious than you allude to.
Stability of government is a perfectly legitimate defence of a first-past-the-post system, but that carries an inevitable democratic deficit - you're arguing for the benefits of constraining the choices of the electorate.
I'm somewhat sympathetic to that argument, but it places a far greater onus of responsibility on our dominant parties. If our electoral system prevents a diverse range of parties in parliament, then those parties have a duty to represent the diversity of the electorate.
In the case of the EU referendum, they have a duty to represent the interests of both the 52% and the 48%. Totally ignoring almost-but-not-quite half of the electorate is just mob rule dressed up as democracy.
On the other hand, the countries with the most stable democracies (measured in centuries) (US and UK) have two-party systems. So maybe the choice was less obvious than you allude to.