This time though, my wife was nagging whilst I was changing it and the Black live returning from the switch got confused with the nuetrals (No Red Sleeves used in my house). So when I thought I had finished and turned the power back on and switched the light on, the fuse blew
Don't blame this on your wife......
that will get you whacked!!!
As you probably know the UK underwent a color code wiring change in 2004. The old colors for single phase
Black = neutral
Red = live
green/yellow = earth
new colors are
Blue = neutral
Brown = live
Green/yellow = earth
Below is a ceiling rose which is very similar to what you should be looking at. If you notice the old colours are in the existing wiring but the new fixture has brown and blue wires. Green/yellow earth has not changed. It is important that you get this straight when connecting your wiring at the rose.
In your case you have a red and black loop to the switch from the rose. black should be your switched live as you indicated (coming from the switch).
However it would not be your incoming power at the ceiling rose a red wire should be doing that job. Please refer to this diagram....
So my suggestions are to reset the breaker in the CU and look at the ceiling rose to see if the power to the other light circuits is correct on the connection bus and check voltage for 250 volts to earth at the live terminal where all power goes on to the other lights. It would appear that you have no voltage on the live terminal in the ceiling rose. Same connection check for the neutrals, which should be black in your case...except for the switch loop where black is being used for switched live. Should have no voltage on the neutrals to earth. As you say your switched black is not sleeved red so be cautious in your connections at the rose to be sure you don't miswire.
Everything being correct then you may have another blown fuse at a spur
in the wiring downstream of your light. This would be in a plug box not a switch box.
Now on another note though creating a ground fault will definitely blow a fuse it also causes massive amperage to flow in the wiring till the breaker in the CU opens. There is quite a bit of released energy that can cause connections to fail. So I wouldn't take this short cut in the future.
In the USA we use wirenuts for joining wires in the splice boxes in your country you use terminals as shown in the diagram, check these for correctness and secure all the wires. No power on the loop of course.