Has she got any small plant pots that she can plant them in to get them started? They don't need a lot or room around them just their 'bums' in the compost.

On a window sill would be ideal. If not she really needs to wait until there is little risk of frost.
Or she can put them in the troughs but cover them if there is a risk of frost.

Hope this helps

Begonias hate hate hate the cold. As Eileen says, wait for the weather to warm up real good. The soil must be warmed up too. I'd wait until May to put them outside. If you have a greenhouse, you can start them a couple weeks early, but then you'll have to acclimate them to the outdoors which is a pain. I would just start them outdoors once we hit May. Also, they don't like a lot of fertilizer. Just give them some rich compost and they'll be happy. They need dappled light. Don't let them sit out in the sun all day - under a tree is perfect, not deep dark shade. Keep the soil evenly moist.

Hmm..begonias are tricky without a greenhouse. Best start them off in small pots on a windowsill, preferably not a south facing windowsill as that would be too much sun. Then pop them outside once its warmer....end of May ish

Thank you all very much. I will let my friend know your thoughts. She is one of those people who likes to get on with a project but I hope your warnings and advice will slow her down! I'm not sure these begonias are going to be a great success, especially as they will not be in shade!