I was under the impression that this had been sorted out. It happened after the new SIM cards were issued. The old ones were re branded EE the new ones appear to be Proximus. However there are still reports coming in regarding 4G not working in some places.
I'll probably get told off but if I relied on roaming then Virgin would not be my first choice. Browse through this forum and you will soon see that a good number of posts a regarding problems with roaming.