Spellzone (www.spellzone.com) is great as it covers/well-adapted to the National Curriculum requirements.
Spellodrome (www.spellodrome.com) is more interactive and more interesting to use for someone that loves using computers. Also, adapted for use on iPad as well. My daughter finds this more interactive and exciting to use.
We use both spellodrome and spellzone. You can trial both of them and figure out which one she prefers or you may decide to use both if you can afford it.