Our fridge freezer is not working,can it be repaired,think the coolent leaked,is it cheaper to buy a used one or get it repaired?

If the motor is running virtually all the time and its not cold at all then its a coolant leak and probably not worth repairing.

If the motor runs but its not getting as cold as it should it might just need a coolant recharge but that's not very cheap these days.

If the motor never runs then its often just the thermostat and can be economical to repair if the rest of the fridge/freezer warrants it (if the door seals are dying then its probably not).

Normally I'd just get a replacement second hand one from Wirral Clearance or similar.

Nothing is happening in either fridge or freezer,lights are on,there is a wire that goes into a plastic circle of about an inch and a half across but it's snapped,it's on the back of the Fridge on the inside.There was a big block of ice surrounding it,I smashed the ice,the wire snapped and that's when it stopped running.

Sounds like you have snapped of the Thermostat.
So the fridge has no idea to go hotter or colder.

Repairing a thermostat as its only a wire sounds easy enough but i bet its part of a sealed unit.

Deffo sounds like you have snapped the thermostat sensor, give grange electric in Oxton road birkenhead a call they may be able to sort it.