Nope - you're not the worst gardener ever, BRT! Believe me.
I'm in exactly the same boat with my tomatoes - lovely healthy green plants, fed and watered regularly, pinched out base growth/side shoots, limited the number of flower trusses etc etc etc, lots of rock-hard green fruits but still only one red tom, and that's on the puniest plant!
I haven't even got any fruit at all on my pepper plants - just the beginings of flowers. Think they'll be moved indoors into the spare room soon (sadly no room for a greenhouse in my garden)....
It's the weather - not enough warmth and not enough light. Outdoor tomatoes and peppers etc are not the most reliable crop in the British climes.
I'm currently doing battle with caterpillars on the perpetual spinach patch - have only actually found one creature itself
, but there are loads of tiny white eggs to scrape off, and endless holes and trails! Still managing to get a fairly prolific amount of usable leaves, though. Grows back bloody quickly, that stuff! 
Carrots look to be doing well, courgettes are still pathetically small
but absolutely delicious
, and still a few broad beans left to pick - they've actually done really well considering it was only a short row of plants. Just finishing off the last of our new potatoes - they were truly brilliant, tasty and a really high yield, so I'm definitely going to grow them again!
I'm contemplating what to sow/plant next.
Missed the boat with leeks, baby turnips and kale methinks
, but have a fair variety of seeds for winter salad leaves and radishes which should yield pretty quickly, and spring onions to sow in September to be ready next spring.