Boiler - pressure problem -now no heating

[Aprilkeogh]

HELP - We are chivering

I topped up the pressure on our Worcester 24cdi but unfirtunately it went to just over three, so I bled radiator till it went back down to 2.5. BUt now heating wont come on. Temp on display keeps going upto 99???? Now i'm stumped.

Do i need to darin the system?? If so how??