Sorry i missed your first post last Monday, Jamie. I wouldn't put them outside yet.They can stand cold, but as they are so young and not acclimatised to this unusually cold weather I would do as you would for young chicken chicks and keep them in until it warms up. I had mine outside in a rabbit run on grass all last summer and they did very well. I only moved them out there because it got too hot in their cages. What sort of accommodation have you prepared outside for them? It's very important that they don't get damp and that they have good shelter from wind as well.
ATM the temperature is dropping very low at night and also the strong cold winds would be very bad for them. As and when you do put them out, it would be best to start by giving them a few hours on a warm sunny day ( remember those?) and then back indoors at night for a while to help them get used to the change. Not worth risking setbacks a this stage, is it, after all the care you have put into them.
Have you been able to decide what sex they are yet?