Frost

I have just checked the weather forecast for next week on Metcheck (www.metcheck.com) and whilst the actual temperatures in my area are not going down to freezing the chart says that on a couple of days it will "feel like" -1 or -2 even though the temperature is above 0.
Does a "feel like" temperature of 0 or less count as frost when it comes to plants, or only the actual temperature?

Thank you for that - seems like they still need some protection until its gone up above plus 2 or 3 then?

I am mostly thinking about my potatoes here = they are in containers and I have earthed them up so many times that the soil is now at the top of the container and I have no more room to put any more. Was hoping that I could get away with not adding any more soil but think I might have to put an "extension" around the side of the pots so that I can earth them up a bit more. Most of the other stuff will not be going outside for another week and those that do I can probably get away with putting a cut off plastic bottle over the top to protect them a bit.

fleece is fine, depends how many potatoes you planted......whether it's a viable option, though.
Great for tubs or the odd row 

You can also lay down newspaper, weighed down with a few stones and removed in the morning, if you have nothing else handy

We've temperatures going from the sublime to the ridiculous - last week it didn't get above 16 and today it's 30+. Overnights are around 18 now so I've moved some babies outside and hope for the best   - the windowsill was getting ridiculously overcrowded with the 100+ baby canna plants that germinated from a handfull of seed given me by a friend in the Azores.  There are only so many cannas a garden needs so I'm giving them away right and left.