If your Panasonic set has the ability to mirror phone screens built into it (
http://eng-ca.faq.panasonic.com/app/answers/detail/a_id/43305/~/how-to-use-the-mirroring-feature-on-a-panasonic-television-with-the-firefox ) you can use ANY Android phone currently on the market. The ability to use screen mirroring has been built into Android from version 4.2 onwards, which means from the later versions of Android Jellybean. Unless you're considering some obscure Chinese phone on eBay, or a secondhand model, you won't encounter Android Jellybean or any of its predecessors, as Android is now up to version 9 ('Pie') for the very latest phone models.
Virgin Mobile uses the EE network and will thus have exactly the same signal strengths as other networks using EE's masts, many of which are far cheaper. (e.g. Asda Mobile). So there's no reason to stay with Virgin Mobile and, indeed, a very good reason (price!) not to. (You can switch to another network and take your number with you. It's a doddle!).
You should ensure that your new smartphone can use 4G signals. (There's not much point in looking for a 5G phone, as 5G coverage is only available in very limited areas of the country; they're also quite pricey. The cheapest smartphones on the market only offer 3G, which can be annoyingly slow, so it's worth paying a little bit more for a 4G phone).
I love my Alcatel A3 but it's now been discontinued. However the similarly-named Alcatel 3 (which uses Android 8, 'Oreo') is very similar and available, SIM-free, for £79.95. Based upon my own experience of Alcatel phones, and the reviews here, I'm happy to recommend it to you:
https://www.argos.co.uk/product/8794521