Thanks for the reply and advice k very much appreciated, I have bought them now and will be arriving tomorrow so will give them a go 1st . If they are no good I will find some of that elastic that you said.
I find that with the elastic you can go round 3 sides of the tent as many times as you want from top to bottom.
With those expando bars you are only covering the middle section of the tent and only on one side so 3 at least are needed to have good effect which works out expensive.
Bungee cord is cheap as chips and you'll get a perfectly square tent from top to bottom.
The door section easy too and once closed its perfect.
Always works for me and you can see it in use here if you look at the white tent sides and there you can see thin bungee cord.
Full capacity of the tent is utilised.