I've been an ardent supporter and user of GiffGaff for years, but as of now, you don't get EU roaming UNLESS you make a connection in the UK, in which case you get the next 60 days of free EU roaming. Since I don't travel to Ireland via the UK, my esim is useless in Ireland next year, so I'll have to find another plan, such as Ubigi. Sorry to lose my longtime UK number, since I actually had it memorized :-(
They changed their terms last year as you've described. You have to have used your phone in the UK in the 60 days before using it in the EU to have free roaming. It works well for me as I travel frequently to the UK, but it won't work for everyone.
I used my GiffGaff paygo sim in May in Ireland, worked ok, but after 2 weeks without connecting in the UK, no more free roaming. Here is a text from GiffGaff with the EU prices and then after my return to the U.S., a text giving the "International" roaming costs.
giffgaff: Hello, your 2 weeks of roaming like at home is nearly up. From tomorrow roaming in the EU and selected destinations will be charged from your balance at 3.2p/min, 1p/text and 10p/MB.
[5/5/24 04:16] giffgaff: Welcome to USA. Top up your account and keep in touch with your friends and family while on your travels. Calls cost £1/min to make and receive, 30p/text and data is 20p/MB.
Too expensive if I were making many phone calls, and crazy expensive for data.
Apparently, this wasn't Giffgaff's idea. The EU issued some new rules, probably as a reaction to Brexit.
I expect to arrange an Irish esim for our next trip, probably through three.ie. Or maybe my US carrier will offer a reasonable plan.