Royal Mail online stamps

Has anybody used the Royal Mail’s online stamp system? Does it work? It seems like it should be great, but I’ve been trying to buy a first class stamp since lunchtime and it keeps telling me – at the final stage of five – that there’s an unspecified problem processing my order. This would be ok, but there’s no way to save address information and the damn thing logs me out after fifteen minutes of inactivity. Given the placement of the error message, and that it’s lasted all day, it feels like I’ve tripped a bug rather than caught it at an off-time. Is annoying.

Update: working as of Wednesday, so must just have been a blip.