thanks gents, and no worries WGB- but it won't be very impressive, just a handful of different abrasives, a drill and an angle grinder (and some beer, but more on that later)

i level most of the welds with a 40 grit flap disc, then follow up with 80 grit --> 120 grit fiber sanding discs in an angle grinder to blend them out (i try not to hit the base metal with the 40 grit so really only do a couple of light passes over the welds to remove most of the stock

next are some non-woven abrasive discs that back onto a hook and loop pad on the same angle grinder, one in medium and one in fine to remove the grind lines from the fiber discs

next is a surface conditioning wheel that chucks into a drill (i use these ones - if links are not allowed, please remove and accept my apologies) in 2 grades, 100 and 180.

to get the mitered polishing effect i run the surface conditioning wheels one way, to set the grind line on one side of the corner, then mask off the middle line with a thin bit of aluminium from a cut up beer can clamped in place. then i run the wheels over the other side of the corner and over the clamped beer can so it creates the mitered polish effect

i will post some pics of the various abrasives and an example of the beer can thing later on if you'd still like- but am currently at work