I asked this question inside a Lebara thread, but no response. So I'm trying again 
We are in Portugal and Spain and are into our second month of 100 Gb for £25 with Popit, and so far, so good. It's been excellent everywhere. Hopefully it will renew for our third month as well.
We used it before leaving the UK, only for a short time, but that was sufficient to "go green" so we could use it in the EU.
I understand on our return we will have to use the SIM in the UK until it goes green again. But does anybody have any experience of how much data / how long we will need to use the SIM back home after 3 months use in the EU before we can freeze it at £1 per month?

We are in Portugal and Spain and are into our second month of 100 Gb for £25 with Popit, and so far, so good. It's been excellent everywhere. Hopefully it will renew for our third month as well.
We used it before leaving the UK, only for a short time, but that was sufficient to "go green" so we could use it in the EU.
I understand on our return we will have to use the SIM in the UK until it goes green again. But does anybody have any experience of how much data / how long we will need to use the SIM back home after 3 months use in the EU before we can freeze it at £1 per month?