Posted: 28/07/2016 at 21:31
I agree with Ladybird. Chillies cross pollinate readily (even with sweet peppers) and there is absolutely no telling what you'll get from plants grown from saved seed, especially if the 'mother' plant was an F1 hybrid (with F1 hybrids, even pollinating with another identical plant won't produce 'true' seeds.) To guarantee the type of fruit you want, grow them from seed bought from a reputable seed merchant.
However, as Pete said they may well get hotter later in the season, especially if we get some more hot weather. Most of the heat is in the seeds so try chewing a few of those on their own - if no heat then not much hope for that outcome.