ferroli modena 80 E ch not firing up?

my ferroli combi central heating is not coming on and it is also taking longer for the hot water to come through. when you turned the heating on there used to be a small click just before it fired up but now there is nothing(no click,no heating,no nothing)and the evenings can still be alittle bit chilly. i assume that when the heating is repaired the hot water will come through as quickly as it used to. anybody got any ideas. i am in the building trade so i have half an idea about these things but this has got the better of me. please help. thanks in advance.