That visa doesn't allow you to work or stay over 3 month. So much for your retirement condo. Hehehe.
From personal experience.
The standard tourist visa, granted upon arrival in The UK, indeed is valid for 90 days. However, once there, one can apply for an additional 90 days and so stay for six months.
There seems to be no limit on the number of 90 day visits one can make in a year though surely there must be something along that line. I've never bumped into it though I make frequent trips to The UK. In more than one instance I've made two or more 2-3 week visits in rapid succession. Once even arriving for the second time within the 90 day period encompassed by the earlier one.
But, yes, 90-days is simple; 180 days becomes a procedural quagmire and beyond that, unless a full-time student, very difficult. Of course no fair working during the time.
And, in other news, Tony Blair has come out for "Remain". That, accompanied by Our Kenyan President's meddling in foreign elections, make it plain that BREXIT is essential!