Bought some 120cm white LED strip lighting from e-bay today. I'll have to experiment to get the light levels right, but 16 strips will get me started. I hope to do 2 strips per 4ft tank.
If it works, this will leave 2 more 4 ft tanks to light up and then I need to think about the 3ft and 6ft tanks. I think they do 96cm strips and these will be ideal length, just need to see how the first lot go. I might have to do 3 strips per tank, but I am not doing display tanks so I doubt I'll need it "bright". Hopefully the LEDs will show up the fish's colours better for photography.