I have a long-standing rule of thumb that a functional smartphone should not cost more than a more capable laptop.

Smartphones in the £150-200 bracket can be reasonable and Wi-Fi calling is considered not a high-end feature, generally managed by installing an App or may be exposed in settings.

I would now buy carrier-neutral unlocked phones and combine with a SIM-only plan preferably with terms no longer than 1 month (PAYG or rolling).

The last smartphone I bought was a Moto G⁵ and that has been ok, my minimum requirements were dual-band Wi-Fi (including .ac) and 4G LTE capabiliity when I was replacing a lost phone (also a Moto).

For my pocket I'd actually prefer if they made more 4 to 4.5 inch mobiles but the trend is towards used to called a "phablet" of 5-7 inches, such that the more compact phones have become more expensive again.

My perception on call tariffs is that fixed-line call pricing has been allowed to creep up while the broadband pricing is front and centre of marketing. The idea that the luxury of mobile per-minute or unlimited minutes would be cheaper than fixed-line call tariffs would have been a laughable notion not so long ago.

That said the UK mobile operators are aligning on higher out-of-bundle pricing too with rounds increases in the past 12 months because they can get away with it if they all do it.
I guess they have to try to recoup the cost of the spectrum auctions eventually. It's far from an ideal model for the market.

In reply to a post by BlizzardUK:

Don't you need a specific mobile phone for that though ? I presume only the expensive phones ? Also I would still need the line rental for broadband, so what I save in paying £10 for unlimited landline calls I am guessing I lose on paying for a £300+ phone ? Or can cheaper phones get it ?

There's me falling for the assumption that everyone has a mobile. Which I know not to be true. So yes, if you don't have a capable mobile and/or an unlimited minutes contract, a landline deal may be better for you depending on your needs and circumstances.