Just migrated away from Plusnet to EE through the recommended path without issue. Not showing off, just want to reassure people that it does happen sometimes!
Only niggle I had was that communication was lacking through the process.
SIM ordered Sunday, page said "SIM will arrive in 2-3 days, number will port in 2-3 days".
Confirmation email (also on Sunday) says "Number will transfer within 24 hours".
SIM arrived Tuesday, put in phone on Wednesday, number transferred successfully Thursday morning.
5G at last! And WiFi calling.