Hi Pete,
Here is how I solved the problem on my XK150S (triple SUs): SU fiber washers and banjo bolt tightening - #9 by clivejer.
Believe me, doing this on an E-Type will be child’s play comparatively; the XK inlet end is also on a banjo so you need to line up 4 connections, and the whole lot is stuffed into a space a mouse would find claustrophobic.
Good luck,
Clive.