Not a brit, so someone else can correct me on this, but there's only been one House of Commons general election cycle since Cameron stepped down. During that election, Corbyn and Labour had significant gains, partly because he was able to excite the left, and it was seen as an election cycle with two main choices: the conservatives and labour.
There's been some sorting recently with the anti-brexit left favoring the Liberal Democrats and the former UKIP forming the Brexit party, so if the election were held now, the results could be very unpredictable, especially with vote-splitting in a first past the post system.
A recent survey in the Times has the four parties at between 19-25 percent. It would be like if polling showed Republicans at 25 percent, Democrats at 21 percent, Libertarians at 20 percent, and some new party at 19 percent.
The next election is scheduled for May 2022, but it might be earlier if there are votes of no confidence or if two-thirds of the House of Commons calls for it (which probably wouldn't happen if the two main parties are both in danger of losing to alternative parties.)