Change/TIG should have just joined the Lib Dems in the first place. The fact that Chuka didn't have the political acumen to make that simple decision before forming the CUK party tells you all you need to know about him, the man is a clown. How long before he has a go for the Lib Dem leadership? One of those 'talented' MPs people speak about, though nobody knows what his talent is.
Once Johnson takes charge of the Tories and heads them towards no-deal, I think you'll see Labour (via conference) go to 2nd referendum position, between their 'deal' and remain (there won't be an option to vote for 'no-deal' in a 2nd referendum done by a Labour government imo). Though it will be determined by a General Election, br0ught about by those Tories who would sooner bring down the government than leave the EU with no deal at the end of October. Tories will have no choice but to campaign as the party of no-deal to get back the Brexit Party voters (and pray that they decide not to stand in a General Election).
Labour will get back a bunch of greens/lib dems who will lend their vote to prevent a Johnson led no-deal Brexit, they will also lose some to the Brexit Party. Tories will get back another bunch of voters from the Brexit Party but will lose voters to the Lib Dems (those Tory voters who don't want to leave without a deal). I think the overall vote share will be fairly close between Tory and Labour, but I think Labour will end up as the largest party as the Tory vote will end up split worse than the Labour one.