I can vouch for 3.
Picked up a monthly contract before I went abroad to roam for free.
The service was faultless and didn’t cost me a cent more than the line rental (data included but not tethering).
There is a 30 day notice period, but I got hard sell when I went to cancel.
2 slight snags:
1) coverage of free roaming is not EU wide. Germany is excluded for example, but Italy France and Switzerland are all in.
2) rental starts part way through a month, so that 1 month period averages nearly 6 weeks.
On balance I’d do again. But now there are other options like Tesco and iD who offer monthly contacts. Although not sure these yet include free roaming like 3.