I've been mucking about with (OK, coping with) these modern new-fangled sonagram things these last 45 years - so, no, not that. I just can't relate what I hear in your recording to either your written description or to the sonagram. So, I'm out.
I am quite sure, this is a Common Redstart or a Nightingale. I am in the Redstart camp, but I would like to hear it on a better device, I cant hear the tak-calls like Butty, too? Maybe we are too old for that? No, I find these things interesting, though I cant read sonogramms, too!
Somehow it just sounds like a Great Tit to me. While the 'tak tak' (which to me is more a 'dzit dzit' 😋) is not very distinctive, the 'ti tui' has the right timbre for Great Tit. But it is a very short sequence after all...
Do you mean too slow or too low? Anyway, to me it fits. The problem is that Great Tits have such a vast repertoire of vocalisations that it is difficult to find an exact match on XC. I don't have much time now but I found this recording which at least covers one of the notes IMO: