Oh, alright then. I was lurking about online a while back and while doing so found a band called Bleach. They were a 4-piece indie band from Ipswich that seemingly disappeared from the public eye around late 1993. This is a song of theirs called Fragment:
The low end is gone, some of the mid range has been removed, and it's pitched down a bit, but butter my arse if from 0:01 to 0:05 isn't the actual sample source for the drums in Sequoia and KFT (It's even got the slowed crash symbol). BOC pages STILL lists the sample as being from Strawberry Fields Forever, the use of which - uncredited - is barmy to even contemplate in a commercial context. When it was put to MDG about the authenticity of BOC's early work, he responded by saying that all the old material is 100% BOC's own, so they may well have re-recorded bits when required, but this is quite close. It's also worth noting that the crash you hear in the Sequoia drums is removed for KFT, so they could have re-recorded that part during the making of IABPOITC.