We stayed there once, we really enjoyed it too.https://www.metzelerttvillage.com/
Admittedly we were lucky, up to the day before we sailed tents were blowing down in the storms, but then it clamed down & ended up the best week for a long time. 
It's not at the National Sports Centre this time tho', it's on Bray Hill.........but not in the road, thankfully!
read about it here -
https://motorcyclesports.net/metzeler-tt...of-man-tt/

EDIT:
Official link -
https://www.metzelerttvillage.com/