TalkTalk are offering 300 minutes and 600MB data for £5 per month (SIM only) - or £3.75 per month if you take out a 12 month contract.
Giffgaff need to compete with this!
No free calls between TalkTalk users as far as I'm aware, and no payback. I wouldn't consider without those features but the headline offer will be attractive to many.
Why do giffgaff need to compete with this? From a business point of view, I would say it's the high spenders giffgaff needs to attract, not those spending a paltry £5 or £3.75 a Month!
Sounds like a real loss leader to me.
If giffgaff were to try to match every network's cheapest deals they wouldn't last long!