UPVC French doors / sidelight coupling advice (please!)

[w44yne]

I am removing our bedroom window & installing a pair of UPVC french doors. The french doors have been delivered & the sidelights either side are separate from the door unit. There are 2 aluminium couplers.
What I have read online has confused me somewhat!
One set of instructions states that I should first clamp the coupler to the sidelight and screw the coupler to the sidelight (from the coupler side) using countersunk screws.
Then clamp the coupler/sidelight unit to the door frame & screw (from the door side) into the coupler, again using countersunk screws.
Then obviously do the same on the other side.
However, posts elsewhere seem to suggest that you just clamp the door frame, coupler & sidelight frame together in one go and screw through from the sidelight frame into the door frame unit(?).
(I think I would have difficulty doing this due to the limited space to get even a small drill into the sidelight frame aperture).
Anyway, could someone kindly please explain the best way for me to go about coupling the sidelights to the door frame? The coupler is aluminium & 31mm 'thick' at it's centre. The frames are standard aluminium upvc coated.

I will try & upload with this post a couple of photo's.
Many thanks in anticipation!

 

[Gazman16]

Best to screw through from the frame sides into the couplers, Both from door side and window side for strength.

Self drilling baypole screws like these will make life easier http://www.ebay.co.uk/itm/4-8mm-x-7...hash=item2cad73dcfd:m:mtmw1NVL7Ynrz1uf_zZj1bQ

Top and bottom fixing 150mm away from the corner welds then approx every 600mm. so about about 20 in total plus a few for snapped threads.
A flexible extension bar or a 90degree angled drill end will help (about £3 from ebay).

Your also going to want to file out the welds on the sides of the frames so the couplers fit snug.
A bead of silicone between each frame and coupler is recommended.

And most importantly of all! A silicone bead along the back of the cill and the 2 ends to bed the frames down onto, Or you will end up with leaks that are always being asked about on here

 

[w44yne]

That's fab - thanks for the response! I'm pretty much au-fait with it all now. Just got to crack on with it!!