BTW in OxfordWest and Abingdon at the last GE the LibDems had a 9500 majority to overturn. It was achieved by throwing everything at it - volunteers coming up from places like Winchester to help out, and the Greens standing down their candidate. So it's possible.
It’s more than possible, it should be very likely.... by-elections traditionally often have huge swings far greater than what is needed.
Indeed, given the number of things in their favour, it would be pretty disastrous if they didn’t!... and to “Remain” in general. The bookies agree giving them odds of 1/5.
If they do win, the key things to look for are:
a) who comes second? Will be a good measure of Leavers’ mood.
b) which one of the Remain vote or Leave vote is higher, contrasting this to the 2016 referendum result (which was a narrow Leave victory I believe). Of course, you have Labour fighting this which will make such a calculation more complex, but I expect them to get comprehensively squeezed into a very low vote indeed.