Ok, so right now your dandrobium is taking a rest. You still need to water it about once a week. Let it dry out completely between waterings. Keep in a warm place & out of direct sunlight. It will wake up again in late winter; hold off on fertilizer until then. When it wakes up, it can take a few hours of morning sun.

This is a very good site and offers excellent advice on all aspects of growing them.
I have used their info before.

http://www.orchidsmadeeasy.com/dendrobium-orchid-care/

ps I love Hickling broad, one of our fav holiday destinations when the girls were little.

I have a dendrobium nobile ( B&Q) for 2 years. I managed to get it to flower again in spring/summer just gone. It is now in a cold light garage as per instructions on the website below. Note there are different dendrobiums so you may need to try and identify yours first before following instructions. see website https://orchid.org.uk/dendcult.htm. hope it helps.

Thanks for this question. I am relieved to see I am doing the right thing with mine too. I keep them on a North-Facing window sill. They are resting at the moment. Hopefully they will wake up in the spring. It's confusing isn't it, because I bought them in full bloom last winter! So I was expecting flowers by now. Everything gets forced.

Dendrobiums like brighter light than Phalaenopsis, so keep it in bright indirect light or filtered sun. The leaves should be the color of a green olive--darker greens usually mean that the light isn't intense enough to allow bloom. It will tell you when it is waking up by starting to grow new "canes" from the base. Normal blooming for D. phalaenopsis--not to be confused with the genus Phalaenopsis!--and D. nobile is late summer into fall, but can be adjused by fiddling wih the day length.