2 gang 2 way light switch

[Davekatentl]

Hi can someone please help I was replacing a hall way light switch for a dimmer and stupidly got wiring mixed up
Downstairs switch is 3 core cable
Blue 1 way
Yellow 2 way
Red common
There is another cable 2 core back and red the black is in with the yellow and red is in with blue I've not touched this switch
Then I've got hallway where now I've got 2 3 core cables 1 from downstairs 1 from upstairs plus a 2 core red and black this is where I'm mixed it up upstairs again is 3 core cable not touched again
Red common blue 1 way Yellow 2 way

 

[Taylortwocities]

The answer is in the WIKI at //www.diynot.com/wiki/Electrics:Two-way-lighting
Please note that the some of diagrams have been drawn with the older cable core colours, others with the new cable colours.
As a rule for these diagrams, RED = BROWN ; YELLOW = BLACK ; BLUE = GREY ; BLACK = BLUE.