Hi there, Dave,
I thought the usual UK urban practice was to wire houses in sequence: red, yellow, blue, red, yellow, blue et seq. down each side of the street. (For recent installations, read black, brown, grey, black, brown, grey et seq.)
If I'm right, you're probably nearer to a three-phase main than you thought!
The above applies to underground mains cables and might not apply to overhead distribution. And I'm not sure about phase sequence with the new colours.
Someone will know!

Hi there, Andrew, you beat me to it again!!