Heater Only Blowing Hot Air- Help

[Marie]

Hello all, I was wondering if anyone could be of assistance to me, I have a 55 plate galaxy and since the better weather has arrived I have noticed that the heater is only blowing hot air(even if the dial is round to cold) Also none of the lights are working in the control panel, so I can't tell if the a/c is on or not, my local garage is at a loss at what to try, we got a new control panel from a dismantlers but it didn't make any difference, but it has two paint marks so we're thinking it's been out before and is not working. I have tried some other dismantlers but they don't have any in at the moment, does anyone have anyother suggestions as to what it could be