First - do you know if there are any cables or water pipes in the vicinity of where you want to put it. Best to know.
Second - can you say if it is a screeded over timber floor or concrete. Fro your post I suspect the latter. Knowledge of the location might help including age of house and ground floor or above. It will make a difference and I'M not going to jump to conclusions.
Third - I'd presume you'll be using 3 x 2 (sorry 75mm x 50mm) timber for the sole plate and I think I'd want to be using bigger fixings than 4 or 4Â½ inches.
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