Hmm...
So I went with XLR>TRS and ended up with such low levels (at maximum gain) as to be absolutely unusable, even after the soundman very kindly boosted them for me from the board. I even unplugged the digital cable and tested the analogue outs at one point but the levels were consistently low.
Like I say, this is a board that I've always had to use attenuators with in the past, so I'm a little unsure as to what might have happened. Could this be consistent with the board using a different configuration for the XLRs than the UA-5 expects (ie something other than 1-gnd, 2-hot, 3-cold)?
Got a decent recording using my mics thankfully, but would really like to get to the bottom of what happened with the sbd feed.
Any ideas, criticism or amusing anecdotes would be much appreciated.