Thanks Licqourice you've been really helpful. I am going to go ahead and order it so watch this space!!
Good luck, shout back if you have any problems (which hopefully you won't).
Having on the 18/6/15 upgraded to Infinity 1 and was in the same situation as you except that my main computer is wired. H.hub5 is connected to a normal extension socket with a filter I get speeds of 38- 40Mbps, I use an android mobile and tablet which are connected wirelessly I can't check the speeds I get on those (don't know if I can) but perfectly adequate for me.
I ordered my upgrade on 6/6/15 received new hub 16/6 and I self installed and was connected on 18th. It was an easy self install and no waiting around for an engineer!
To conclude I am very happy with my Infinity 1. lt was all stress free.
Thank you Patty that makes me feel a lot more confident - have been given a date of 26 August so here's hoping it all goes as smoothly as yours.
What a godsend this forum is - thanks to all who replied.