It used to be a Oz based company behind it, any +44 is classed as UK unlike our great UK telcos
The £3 credit expires, unless you top up before the 6 months are up. If you top up again, the original £3 won't expire for another 6 months. So long as your credit doesn't expire, the offer goes on. And you'll keep building up credit.
Can't see this deal on their website? What happens after 6 months, is it another £3 or more?
Only if you use their dial through number. Calls on WiFi or mobile data don't incur a connection fee.
No, it's completely separate from Tesco mobile. Anyone can use it.