I assume you are talking O2 Home phone + broadband.
P2P is a no-no on O2, but that package is reasonable if not.
See the FUP and throttling applied to the various packages on this page
Note two things about the costs.
The three-months free is supposed to end tomorrow, but has often been renewed. Also if she has an O2 mobile phone then by ordering through TopCashBack or Quidco she can get up to £90! (Remember to clear cookies
before going through to order).
A PAYG mobile earns the £5 discount off broadband, yes.
My broadband basic info/help site - www.robertos.me.uk
My domains,website and mail hosting - Tsohost
. Internet connection -
IDNet Home Starter Fibre.