Hive tends to replace both the programmer and the thermostat. As said likely to replace Hive with a programmer will be easy. Just slack off two screws and unplug, and plug in new, and re-tighten the two screws.
However the back plate comes with three wiring configurations that I know of, single channel, twin channel and three channel, although latter is mainly Drayton Wiser Hive does not as far as I know do a three channel version.
I would not really call any thermostat standard, we have the mechanical on/off with anti hysteresis compensation,

and for very little extra a programmable one

battery powered. But neither fit on the back plate, I like the idea of simply turning a dial but this

is hardly standard and more complex to the Hive it replaces.
Likely looking at minimum charge to fit it, but one wonders why? The thermostats around my house are mainly programmable

and I can see when fitting them how a wall thermostat has very little to do, and could well be replaced with a programmer (timer) or very simple thermostat.
But main reason to down grade a thermostat is to take it with you when moving house, I in fact swapped most of mine before selling my mothers house

mainly as buyers did not want them, but it was simply a case of unscrew one and screw in replacement, and £6 for mechanical and £50 for Hive with this house having 14 of them I can see the point.
But for the wall thermostat I see Hive for sale at £60, so not really worth the hassle to change.