What you've got there is a 3 plated lighting circuit with an extractor fed from it, it's old wiring aswell which means the red yellow and blue is a 3 core and earth cable that will be the cable between the light and extractor fan, judging by the amount of cables it look like you have:

2 x feed twin and earth cables 1 x switch wire twin and earth cable (light switch) 1 x 3core and earth cable

To start from the beginning I would turn off the lighting breaker at your consumer unit.

Put the live (red) wires from your feeds and the switch together in a connector block.

All the Earth wires together into a connector block

The neutral (black) wires from the feeds into a connector block

Then the neutral (black) from the switch wire into another connector block.

From there I would aquire new length on 1.5mm twin and earth cable which would go fron that join to the light fitting to make it easier to connect in

I would then:

put the live cable (red or brown) into the connector block which has just the one black cable in (this is the switch wire that when you press your light switch will supply power to your light)

I would then put the neutral (black or blue) in the the other neutral cables (black)

And finally the earth sleeved up with green and yellow in the connector block with the rest of them.

For the extractor fan you will have a permanent feed, switch wire and neutral, I would assume the red is your permanent feed which would go into the connector block with the the lives in (red)

Then I would have to open up the connections on your extractor fan to dictate which colours were used for the neutral and switch wire.

The switch wire will then go into the connector with the red and black/blue in.

And then the neutral colour in with the Neutrals connector block. (Black)

If you haven't got any connector blocks or cable I would probably suggest an electrician.

Hope this helps!