As far as I’m aware there are no 6GHz consumer routers on the market at the moment. All the WiFi6 routers out there are only 2.4GHz and 5GHz.
You only get the full WiFi6 speed on 5GHz if you have compatible WiFi6 clients and access points. But it think that’s fairly obvious.
The only WiFi6 unit I’ve tested personally is the TP-Link Archer AX6000 and it wasn’t fabulous for high speed and good coverage. 2.4GHz coverage was shocking and 5GHz coverage was fine but as soon as you enabled the WiFi6 features to get the speed you had to be fairly close to the access point (5-6m).
I think it’s too early to invest in WiFi6 at the moment. Give it a year and the market will be much more mature.
And I don’t think you’ll get a WiFi6 router under £250 yet. If the SH2 isn’t actually broken then I’d be tempted to use it.