The selection of leaded rectifiers available is not huge but I found a Vishay GBPC3512W which can handle 35A and 1200V. I lose a little on the voltage overhead but I suspect 1600V was overkill anyway. The package has a similar thickness but a different pin out. The following is what I plan:
If this doesn't work then I may have to try and make some weird intermediate PCB from copper sheet, sounds like a recipe for disaster. While I wait for the rectifiers I'll check the rest of the board, I may even try "booting" from the remaining rectifier, if all else is well it should work and if it blows it shows the problem lies further in.