Andrew is correct. Channel numbers are given in chronological order. The oldest have the lower numbers, the newest the higher ones.
When Sky Digital launched the exsisting channels were given places depending on their popularity. Hence it went Sky1, UK Gold, Living, Disney, Family/Challenge.
Each channel is given 3 EPG
positions so they can launch sister channels (hence SKy1 is on 106, UK Gold 109, Living 111) .
Any new channels are added in the next empty position. The problem with this is that channels close and move, hence the huge gap between UK Drama and S4C and the gap Disney vacated with was taken by BBC3&4.
In this reshuffle, the companies involved were given the option of moving or staying. Those that stayed get overtaken by any new channels launching after the reshuffle. The ones that have stayed are those who have more to lose by moving than they do by staying put