"The concensus seems to be that you can't go SVFR in class E, only IFR so in this context that simply means staying above MSA (as the transition alt. is 6000ft. and we'd be below that). Does that seem reasonable ? "
It's not quite that restrictive. There's an exemption from the minimum altitude rule if you are below 3000 ft amsl, clear of cloud and in sight of the surface. I believe a minimum visibility of 5 km at night has been recently added to the exemption.
So if you're clear of cloud, in good vis and below 3000 ft, there's no [/b]legal[/b] requirement even to be above the MSA. That doesn't make it smart to fly at low level of course! But if you have controlled airspace above, it may open up some otherwise unavailable routes.