I had a message today (thanks Chris!) suggesting I flesh out the detail of the repair as, understandably, folks are going to be nervous spending a grand on something that has a previous fault. Symptoms were: I followed the usual cold-start procedure - switched on the power with the stand-by 'off', left it like that for 5 mins or so then turned 'on' stand-by - this was accompanied by a smell of burning and smoke! Turned off, unplugged, used back up.
I took it to Electronic Music Services in Southend who are pretty much the 'go-to' industry standard amp techs in southeast Essex. Below is a scan of their report/invoice, which shows they were pretty thorough. I've used it maybe half a dozen times since then but find the whole thing too heavy to manoeuvre around.
Hope this goes some way to instill confidence that this was sorted out correctly by people who know what they are doing.