The pilot won't light?

We turned the gas off about 3 months ago when a house was left empty, the boiler was fine before we did that, now the pilot will not light. We have tried to 'bleed' the air through by holding down the square button as instructed on the boiler, but in spite of holding it in for a long while (at least an hour on and off) there is no smell of gas and the visible spark that is produced by the sparker doesn't light the pilot. We know the gas is working because the gas cooker is alright. We can't light the boiler without the pilot being on. Or can we? ( perhaps that would pull the gas through and pull the air out of the pipe.)
The boiler is an Apollo 15/305. Any ideas?