Thanks Whistler for the heads up on Royal Canin.. I've ordered the smallest amount I could find from an online seller - but that happens to be 36! Annoyingly, it's of the duck one, as I read somewhere this was easier to digest than chicken (can't remember where I found that info now tho! Will just have to hope that Logi gets on with it better than yours!
He's never not eaten anything we've tried, so I don't think he's too fussy. He's not had the squits for a couple of days, so fingers crossed he is on the mend!