OK so the reason I thought 433Mhz was not good enough is because the rf modules sold for arduino only go for about 10cm
Seems an odd conclusion then that all 433Mhz modules are low range.
but that would obviously be because of the power and not the frequency
Not 'obviously' the power at all. How well a module works, and its range, is mainly a function of the modulation type and the receiver.
As @bluejets suggests there are heaps of tutorials out there on doing this and even complete radio control systems based on the Arduino Pro Mini.
However, I would suggest you use purchase a ready built system, designing and building your own so that it is safe does require a fair bit of understanding of things RF.