Surprised EE won’t match the deal, if they say you can’t take your number maybe there is some weird agreement between Metrophones and EE whereby they can only sell new numbers?
Have you checked Three, Vodafone, and O2? If you can find a decent deal on any of them see if EE will match that. I recently moved from EE to Voda, only because the EE signal at home is useless and it’s more of a problem now I work from home all the time. The retention team were very friendly and would have matched whatever deal I’d found, unfortunately they couldn’t put a mast up nearby 🙂
Handsets – I got an iPhone 12 mini as I’m not a fan of big handsets. As above, same size as the old SE, 5, etc. Much better (for me).