EU referendum, brexit and the aftermath

labour voters were more likely to be Remain, UKIP obv. super likely to be brexit

I've seen this comment, or similar, mentioned several times over the past few days. For instance, posts referencing the Ashcroft poll and the statement a few pages ago that portrayed Corbyn in a positive light because he delivered a 64%(?) remain vote among labour supporters.

However, I'm wondering if this isn't a distorted picture, and somewhat reminiscent of the classic tale of survivorship bias in WW2 bombers. Over the past few years support for UKIP has grown enormously, stripping members from both the Conservatives but also Labour. Focussing attention on the number of extant Labour supporters who voted remain ignores the (presumably large) number of traditional labour supporters who have already defected.

I would be more interested to know how many current UKIP supporters would traditionally have identified as Labour, and how this would affect the balance of leave/remain if these voters were added to the current labour supporters.