Temperature in a simmering oven

Hi. I have made Delia's Classic Christmas cake for years, in the Aga simmering oven. To test to see if it's done I try the skewer method and listen to it. Sometimes it's perfect, occasionally a bit over done. I have a digital thermometer which I use on my lighter bakes, including Delia's carrot cake and the cooked temperature is 210°f. Is this the same temperature for the Christmas cake?
Thanks,
Barbara Charlesworth.