Frozen pipes - how to defrost?

[CeliaChristmasFate]

The cold water feed to our utility room is frozen. There's a radiator in there that's on, I've also got a fan heater next to the pipes that's been going for the last 2 hours. Still frozen solid. I'm unable to use my washing machine and will have 2 million loads to do tomorrow if it doesn't thaw out! Why isn't the heater working? Do I need to do anything else?

our waste pipe for the dishwasher keeps freezing at the moment.
i go at it with a hairdryer. it's also lagged with that foamy tubing stuff you can get in b&q etc. just doesn't do enough when the temperature stays below 0 for long.

no idea about indoor pipes but lagging them might be a good idea.

we had frozen pipes last week and hubby sat with a hair dryer and electric heaters till they thawed out. the boiler then burst a pipe and flooded the kitchen a few hours later! the whole house was frozen up though after a weekend away and a power cut.

just over heated my hairdryer faffing with the bloody thing!