[mumofstig]

the simple ones just raise  the temperature by about 8-10 degrees above ambient.
The expensive ones usually have a thermostat so that you can set the temperature - i've never usued one of those.
Cheap and cheerful rules here 

[JohnB47]

Fair enough.

[rachelsco]

i have not got a heated progagator but after no sucess after two attempts, i put two in small pot of damp compost with cling film on the top, this i put on my pc router where it is noce and warm. about a week later two shoots popped out. i was so pleased, because they were the yellow ones which are gorgeous.  try this method, it might work for you too

[compostqueen]

Oh yes    The £14.99 ones are as you'd expect bog standard and come with a pre-set heat. The dearer ones have thermostats on as some seeds require different temps to germinate
I've only ever the cheap ones but they're fine 

[arugula]

Perhaps we should have a new topic on heated propagators.

[compostqueen]

Sorry..   Slaps wrist 

[mumofstig]

me as well 

[arugula]

Go on then!