I had success simply germinating the seeds out of a chilli I bought from the greengrocer, so provided they haven't been sterilised to extend shelf life it ought to be possible in theory to pick your favourite variety and grow it. It would of course depend on whether they are produced from an F1 hybrid plant or not, but the three different types I've tried so far all seem to produce fruits identical to the original from which I got the seed -- the two dwarf varieties both produced dwarf plants of the appropriate colour, for example.

I don't like hot chillies, so I normally'dilute the effect by using a single miniature chilli to a whole pot of curry, for example, or by chopping up larger varieties and using only a quarter at a time. But if you're a connoisseur and want a specific 'fruity' flavour as opposed to just the hot sensation (I can't really judge the difference!) then it might be worth paying for specialised seed.

I do get the impression they are pretty much at the extreme edge of their range when grown outdoors in Britain, and would probably be more reliable in a greenhouse or a well-lit window sill if at all possible -- not an option for me, unfortunately, as my windows have next to no sill to speak of (enough for a single yoghurt pot's width on the uncurtained kitchen window...)

(Apparently people have now developed *grafted* chilli seedlings for sale, so that you get an earlier, more vigorous crop that grows under less favourable conditions... but of course those qualities definitely can't be propagated on to the next generation by simply saving seed! https://hub.suttons.co.uk/gardening-advice/how-to-grow-grafted-pepper-and-chilli-plants )