1) For ease of carriage, Bellhill had removed the metal frames at the top/bottom of the tent. this does make it rather more difficult to fit so,if you have the option of collecting your replacement tent, it would be worth doing this & installing the complete unit.
2) The tent has a piping along the edge, which slides into a channel on the edge of the frame. The top frame is easy enough, but the bottom one is a lot more tricky - especially the front section, which has to slide around the "corner" of the tent perimeter. I found that the metal tends to take shavings of rubber off the seal. Copius applications of silicon lubricant help. The bottom frame is pop-riveted together at the corners, so you need to drill the rivets out & then re-rivet after assembly.
3) The "screws" holding the bottom frame to the van roof are plastic & easy enough to undo. Screw out, push back in.
4) As reported elsewhere, by others before me, the top screws are loctited in & can be VERY tight. The screwdriver needs to be a perfect fit (posidrive No3 - I think). I used molegrips on a couple to break the "seal".
5) Space is tight on the top corner screws. I rightangled screwdriver was very useful for replacing them.
The whole job took about 4 hours.
I knew that Bellhill had one & they're not that common on ebay, so really had to go with grabbing what was there at the time!