Metal strut across conservatory corner

I need to brace across a right angle corner of a DIY uPVC conservatory. The brace will be just above head height and will run horizontally from near the top of one wall across to near the top of another. The purpose of the brace is not really important but has to do with a heavy door that has to open in a particular direction and be hung from a particular place on the wall.

The brace will be in compression. It needs to be about 4 feet long, round or square section and about 1cm diameter.

I can make the brace from steel tube with the ends squashed flat and drilled, but I can't find suitable brackets for fixing neatly to the uPVC at each end.

Anybody got any bright ideas?

What will the compressive force be? If it's 4ft long, 1 cm in diameter, that seems a little slender.

Not very much, I've put steel along the top of the wall that needs bracing, and that does most of the work, but just need a little extra to make absolutely sure that wall won't move when the very heavy door opens.

As its a tube in compression, something like a plate with a peg sticking out of it would do. Like the peg brackets from this :- http://www.screwfix.com/c/building-joinery/casement-stays/cat841022. Cut the steel of at the right angle (oops I mean 45 degrees at each end). Plodge a bit of polyester filler in each end of the tube and push brackets (suitabley aligned and jigged up) on, leave overnight to harden. Clean up with some emery cloth, paint with primer and white gloss. Mount the brackets vertically, if you mount them horizontally, the "inside" screw hole will be obscured by the tube.
Frank