I reckon, time for
Frank The Chilli Taster to get another airing!
Honestly, what's this with wanting to get at the hottest possible scoville rating? In a decent dish you should be able to savour the
chillis for what they are, not just react to the capsaicin burning! Ah, never mind....
Arch, try using fresh chillis for a change - I'm sure Sainsbury's have them. Thing about fresh chillis is, they're more unpredictable and variable in strength, so you could be in for the occasional surprise. All adds to the fun!