the minimum effort assumption, based on the digrams is
At the ceiling,
the 2+E (red black and bare sleeved as earth) are power (unswitched) in from the supply and on to another light fitting.
The other wire, 3+e (red, yellow blue and bare sleeved as earth) with some cores sleeved as red
probably goes to the first 2 way switch.
The first to way switch has the 3+e from the fitting to it, and a pair of 3+E to the second switch.
Does that look mechanically like it was the 'easy option' for the installer, given the layout? If not then what follows, based on that assumption is not going to be true.
i think what you have is 2 separate 2-way circuits, using the A sides of the switches for one circuit, and the B sides for the other. Then, the 3 plus E is used to get from the switch to the ceiling rose with live (red) from rose to switches and switched live (circuit A) on blue and switched live circuit B on yellow.
To be sure, we need to give the 3 identical 3 and E's at the swithc one names like 'to cieling', 'A circuit' and 'B circuit' and at the 2nd switch ' A circuit' and 'B circuit'From your drawing it is not possible to be sure, but
i jhave assumed that the red/blue/yellow from the same cable go to thee same side (a or B) of a given switch.
The other question. Before you took it down, did both 'left hand' (or right hand) sides of the two double switch control that lamp, and what did (or do) the other sides control? - if 'nothing' it may be that circuit (A or B) was always floating, but an option for a fitting with more than one lamp for dim/bright/really bright options.
we are part way there.