Thanks for that , I spent a whole evening trying to figure out if the 1.4 was supposed to be sqrt(2) and I couldn't find anywhere that definitively answered the question. In the end I assumed that people used 1.4 because after smoothing the average value of Vdc will still be slightly below Vmax (the highest voltage coming through the rectifier).

The next transformer "down" is this 24+24 model then below that is this the 22+22V. The mains in this house is normally around 235 to 237 volts so yes I would be a bit over-voltage. Does the output voltage change linearly with the input voltage? I'm thinking 235V into the 25+25 transformer would produce about 51V out (wired in series). Wish I'd put together a spreadsheet for the calculations now! Considering there's a 2.2V drop in the rectifier I think the 24+24 is probably the best choice in that case - I suppose I've just got to go away and crunch the numbers again.

I'll scrap the relay for the bleed resistor. Considering the price it would take 100 years to pay for itself in the electricity it saves.

I was thinking of trying to put a fan in the case as I have loads of 12V 90mm computer fans kicking around. I don't know how to power the fan from the circuit I have though. I only need a couple of watts so even if the way I get the power is really wasteful I don't suppose it'll matter.