In much of the UK (presumably in the far north it wouldn't work well?) the way to get tasty tomatoes from mid- to late-summer would be to grow them oneself... Of course during the winter tasty fresh tomatoes are unavailable.
Indeed, I wonder how hard those complaining have tried to use local UK produce in season. Go to a restaurant that serves good food using local produce. I do this when I can afford it - I've had some fantastic food, comparable to anything elsewhere in Europe, and some UK fruit and veg is amongst the finest available - a couple of examples - British asparagus, and Yorkshire forced rhubarb - amongst the best available anywhere.
Our winter vegetables are great as well. Leeks, Parsnips and Chard are all delicious.
Oh god roasted parsnips! So good.
I tried that strategy here in the NL and got very nice looking tomatoes but still, watery and tasteless.
There is just not that much strong sunlight during the spring months to bring the taste out.
I guess it's worse in greenhouses which is where most (if not all) tomatoes are produced here.
Second this. Choose a good variety and plant in good soil and you will have lots of amazing tasting tomatoes, especially cherry tomatoes are super sweet if you let them ripen. I have been doing this for a few years in London and it's always rewarding - will grow a bigger batch next summer.