This was not the question asked by the original poster, but..
gatbusdriver
if airfield is Cat2/3 then we require a Cat1 alternate within 1hr single engine flying time
...is not true (unless your company has stricter requirement than EU-OPS). Weather just have to be above applicable landing minima at take-off alternate 1 hour after departure. Therefore you may well use the minima for a CAT2/3 approach, if available.
Also not true, since the metar is just exactly that
an actual. Unless of course you are able to depart at the exact time the meteorologist juts his metar down.