I'd likely think you'd bought it off vinted, not spent £300 for it! If you ski often and will use it, then go for it.
I agree with the above posted about the loo issue though. Ski toilet floors are always wet so you'd need to ensure the sleeves don't drag on the floor when sitting on the loo. This is whilst also holding your gloves, googles, getting toilet paper etc. I vividly recall an Italian resort where the mountain toilets were squat style- not even a seat. I never wore a one piece since because that was a lesson in flexibility and balance.