It's arguable how much that helped, though.
ETA: To expand...
In 1981, the Gang Of Four left the Labour Party (second to the Conservatives, at the time) to form the Social Democratic Party. The didn't like the official Labour direction being too Left Wing (c.f. Corbyn), espousing Unilateral Nuclear Disarmament (c.f. Corbyn) and exiting the European Economic Community (c.f. ...well).
They fought ?two? general elections in alliance with the Liberal Party (the original non-Conservative main party that became squeezed out into largely 'also ran' status between Labour's formation and circa the 1930s*) that made comparatively little headway into power in the Tory-dominated national levels of governance (Thatcher's era), before split-merging to become the Social & Liberal Democrats (now just Liberal Democrats), to be the mostly 'also rans' and - for a time - leaving the original SDP remnants to be 'also also rans'
The Conservatives kept hold of power, even (especially?) without Mrs T at the helm, until Blair turned Labour into an attractive leftish-but-middle-ground-facing party that doubtless took back much of the Liberalish middle** and left-leaning Tory voters.
Labour's not-so-left direction lost internal traction (Blair stepping down to Brown) and disaffection with both current-Brown and the Blairite recent past may have led to the situation where Labour lost, but Conservatives did not win.
Then the Liberal(Democrat)s had influence, but more than two decades after the Labour-split and all the rest, and they worked to support Cameron (as per the end of the * footnote), and in the process lost credibility.
Right now they're acting as the anti-Brexit party (not that either of the main two are pro-Brexit, they're just being both led as "not anti-Brexit at all, just anti-(OtherParty)-style-Brexit,, 'cos their Brexit won't work!"), and their failure to make headway in the last General Election (and also the decline of the Scottish National Party from their heady heights of Scottish dominance) has been taken as proof that "most people voted for a Brexit Party", though it's more like "most people voted for a Big Two party that they thought could best counter the other Big Two party that they didn't like more". As per usual.
But then UK politics (party/representation-wise, among other ways) is nothing like European politics with mass (and often Rainbow-)coalitions of expediency, or else doing as the Belgians did and not having a government for over 500 days in 2010-11, during which time things seemed to work out fairly well anyway (c.f. US Government Shutdowns for a few days at a time!).
* There had been "Lib-Lab Pacts" during the early part of the 20th century, helping Labour gain its foothold and then giving it its first two governments by pseudo-majority. A further LLP happened in the '70s to stave off the Conservatives (though that led directly to Mrs T, either causally or incidentally) and there maybe would have been one in 1997 if Blair hadn't been so successful. We saw what happened in 2010, and the otherwise possible LLP would have needed a few more allied seats from elsewhere (less than the DUP alone had to give the Tories, recently!) to make it work.
** For USians: in UK politics, since the rise of Labour (socialist or otherwise), "Liberal" has been considered the de facto centre-ground term, the barycentre around which all other greater party masses orbit, though the Blairite Labour party was at times and for some issues leap-frogging over the centre and almost Conservatively-rightwing.