I agree that ~ 50hrs/year is perhaps the minimum for good currency, although the preparation can be a lot less than 1-2hrs with computer flight planning tools. One can prepare the stuff for a simple VFR flight in well under 30 mins, including notams, weather, printing everything out, etc.
However, 50 hrs is way more than the average UK PPL annual hours... so what does this mean? I don't think one needs to be doing 50hrs/year to be current enough for a very simple plane and flying down the beach on a sunny Sunday, and a lot of people do just that.
Anyway, one can't compare flying with driving.
At the technical level, a plane is a bit like a car from before WW1 - lots of knobs and levers and gauges, and you have to know which knob does what.
At the "driving" level, a plane is a lot harder to drive around than a car. It has long bits sticking out each side, and if you bump into another plane's bits, they will absolutely love you because, at long last, they can get a brand new wing on your insurance (£20,000). Driving a plane around on the ground is IMHO the riskiest (in "instant hassle" terms; people rarely inside the plane rarely get injured) part of flying, and accidents are very common. As are prop strikes, by going into a pothole, etc... another £20,000... Also planes have crap brakes and crap steering compared to a car. Getting airborne is quite a relief!
At the "flying" level, a plane is easier than a car because with a car you have to pay attention constantly to the road, roadsigns, TomTom etc, and of course other traffic. A few seconds of inattention is instant death, most of the time, on a busy road. With a plane you don't need to concentrate anywhere like that because 99.99% of the time there is nobody else within miles. I can fly for 7 hrs and feel fine at the end (though the engine noise does cause tiredness, as would altitude flight without oxygen) but if I drove on busy roads for 7 hours I would be totally sh*gged. In a plane, the attention instead goes on monitoring the engine and systems, ATC comms, but apart from talking on the radio there is almost never anything that needs urgent attention. It's very relaxing; you can sit there enjoying the scenery, taking photos, making movies, eating lunch, etc.
The big mistake some make is thinking they can use a plane like a car, for commuting. Flying is strongly weather dependent. But that's another story....
BTW, I don't think joining circuits at busy GA airfields (e.g. Stapleford or Wellesbourne on a sunny Sunday preceeded by weeks of bad weather) is ever going to be fun. I have over 1k hours and still hate that stuff. If everybody flew by the book it would be OK but many don't; you get cut up on the inside from both sides, and often one has to go-around because the cowboy has misjudged it and ends up too close in front of you. Due to personal circumstances I do most flying on weekdays and actually I am not unhappy about it.