I received a small 3 tier polythene greenhouse for xmas and want to use
to grow some seeds of which I have many this year.

I put it up and check the temp in it and it was only around 7c at
approx 4 pm in the afternoon.

If I put seeds into unheated propogators with this greenhouse will this
be sufficient for them to grow or will it be too cold at the moment ?

I was trying to get some sweet pea seeds going before it's too late and
the apparently only need around 10c - 15c

I was also going to grow geraniums in a heated propogator which I can
plug in and leave in the green house as it has an electric point right
next to it.

or should I look at some sort of heating for the greenhouse but given
that it is small and polythene what would be suitable to heat it with.

I am trying to keep the seeds outside in the new greenhouse to protect
them from my wife and children who don't give them as much regard as I
do !!!

suggestions please or do I just need to wait until it's warmer to use
these greenhouse ?