Light fitting change - blows out some lights in other rooms?

[Kve]

Hello everyone, I am helping a friend of mine change a light fitting on the his upstairs landing. We had ensured the light switch was switched off. In the surrounding rooms 3 bedrooms and one toilet the lights were switched on also. His house had old wiring (and old type fuse boxes) so I had told him to remove the pullout fuse related to the upstairs lighting circuit. Unfortunately as he was multi-tasking he wasn't paying attention and removed the downstairs fuse, so the upstairs fuse had not been pulled out.

As we removed the light fitting and removed the wires from the fitting there was a small spark and the lights in 1 bedroom and the toilet have died. We replaced the bulbs with working bulbs in the toilet and the bedroom where the lights failed but they do not work at all. In the other two bedrooms the lights are working fine, even though they are all on the same circuit (ring) - confirmed by pulling out the fuse related to the upstairs lights.

The toilet has also got two of the same lights. One has a bulb (which blew) and another one didn't have a bulb. We put a working bulb in the light which didn't have a bulb it doesn't work.

Has the removal of the old light fitting somehow blown something? Everywhere else in the house it's all working fine. On the upstairs ring some lights are working, and one bedroom and one toilet isn't? What could be the issue and what should we do?

The house has old wiring system of wiring with old pullout fuses. We have taken out the upstairs lighting pullout fuse to be totally safe.

What is also weird is that on the light fitting we removed (on the landing) there are 4 wires. 3 of them are coloured black and one is coloured green. How do you connect a modern light fitting to this type of wiring?

We would really appreciate it to understand what has happened and if there is any thing we can do to tackle the two problems
i.e.
1) why are the lights in one bedroom and one toilet not working and what can we do about this
2) how do we connect a modern light fitting to ceiling light wiring which has 3 separate black coloured wires and one green wire.

Thank you in advance for anyone who can shed some 'light' .
Kve

[spinlondon]

Lights are normally wired not in a ring, but as a dasy chain, or spider.
If you disconnect the wires to a light fitting, along the chain, all the lights further along will also be disconnected.
You have to either replace the light fitting, or connect up the wires, to bring the other lights back on.

[davey-s01]

I Think you need to call a sparky as you have mis-wired something and obviously are not really that competent.