You'd need to completely avoid the 1947 Woolton-Tevoit Agreement that made the National Liberals wholly subservient to the Tories; prior to this, the National Liberal Party was in a total state of disintegration, and would have barely survived as a force separate from the Liberals for another parliament (despite having more MPs), which resulted in reunions and remerges on local levels- the most famous example of this was the London Liberal Nationals folding back into the London Liberals in 1946, although these mergers notably failed to get any MPs on board.
Davies was also a bit of a bugbear for some- he was on the left of the party, having left the National Liberals during the war, and was unable to convince those in the NLP to come back as they viewed him with suspicion, despite his and Henderson-Stewart's efforts to negotiate merger. Liberals also saw the NLP in a negative light- Tories appropriating their image, basically.
That said, had Davies and Henderson-Stewart negotiated a settlement that would have seen a unified Liberal caucus reborn, while the nadir may not be as bad as IoTL, it's likely the Liberals will align with the Tories and eventually become their Co-Op, if that makes sense. IIRC, Macmillan famously assessed that it was not until 1959 that the Liberal Party began to take votes back from Labour, so the Tories would have it in their interest to get the Liberals on side for a broader anti-Socialist front. While not the Woolton-Tevoit Agreement, certainly a pact of some sort as was seen on a local level with Liberal MPs such as Donald Wade, Roderic Bowen, and Rhys Hopkin Morris.
Perhaps Davies simply not being leader post-1945 would do the trick? Sinclair either keeping his seat, or some talent who could have helped with a reunion survives 1945.