Can you actually get more than £7.82 worth of calls, running 2 calls (the maximum T-Mobile allow I believe) 8am-6pm Mon-Fri?
I believe the £7-82 pays for 500 texts and 600 X-net calling minutes, with the unlimited landlines booster as something on top Dave.
I know from Graham that their landline booster is truly unlimited, and that he has run up 15,000 minutes in a month himself. That sounds quite good value to me.
And although a certain service which you might have in mind can only be called between the hours you mentioned, there are other services which can be used in the evenings, or even at the weekend possibly. I will leave it to you to do your own research.