The EU requirement is for roaming for 60 days at no extra charge.
If you want more than 60 days, then:
it's reasonable to ask giffgaff to look into providing a special package that works in EU and works for a longer period, but
giffgaff has to pay the roaming partner for the service and therefore
you should expect to pay at least a little more for the service.
have no idea what we will do for data after 60 days
Actually, its already possible to continue using goodybags beyond 60 days -- by paying an EU-permitted supplement of 3.2p/minute, 1p/text, 0.6p/MB which has to be paid from credit outside your goodybag -- https://giffgaff.com/top-up
I believe the EU-permitted supplement is only slightly more than the EU-capped price that the roaming partners can charge giffgaff -- so that's a fair indication of how much extra you should be willing to pay if giffgaff were to provide extended roaming.
But probably there would be little point -- you might just as well continue with a normal goodybag and pay the supplement.