Hi there, it's horrible, isn't it? I've been on tamoxifen since April 2018, and get plenty of side effects including the hot flushes. Mine only last a minute or so, but I can have a dozen a day. The heat in overwhelming and is almost like a panic attack, but then it's gone and I am left with a bright red face and frizzy hair! 

What got got me through last summer was the following: a fan at floor level beside the bed. When I got too hot I would stick my feet out the bed and cooling them would help with the rest of me. I would also relocate to the settee in the living room quite quickly after I started to get hot, and I used a duvet cover with no duvet in it as a sheet.  Some people use a cooling pad, or a 'chillow' I think it's called, but I haven't. Hope this helps.