Hiya matey,
Didn't do any barrows no...
Well apart from long distance ridge hump spotting and mound spotting as we drove. I wasn't aware of any chambered tombs on Exmoor tbh and unless they are massive I tend to limit my tomb hunting to those now...
Re the access, am I right in thinking you have one of those 3 wheeled 'off-road' chairs? You'd have no problem with one of them for most of the sites we visited. Not sure about in winter though, as you know the moors tend to get a bit boggier then!