Small pointed evergreens like Cupressus Goldcrest varieties are bright lime green and can look good in pots. They grow quite slowly and can stay in pots for a year or two. Not everyone likes these, but I'm sure there will be lots of other suggestions. It would help to know the size of the pots you will use and where you are in the country?

I was going to suggest Bay trees - but it sounds as if it might be a bit of a wind tunnel, so if the area is exposed to cold winds all winter, not a good idea. A lot of plants will not appreciate cold winds all the time in winter, including,unfortunately, the Goldcrest suggested by Ojibway. If its not a wind tunnel, they'd be quite good for a couple of years, reasonably priced as well, but they do prefer a bit of sun.
If it is windy, have a look at Chamaecyparis varieties (C. nana albo spica and other smaller ones) or the Pinus group - Pinus mugo, whilst not a dwarf, is very slow growing and will only make 3x3 in ten years. Both these groups of plants tolerate less sun and, more importantly, wind.
Otherwise, for a windy spot, Hollies are good - but not exactly child friendly.

Thanks, wind isn't too bad as the house is an odd shape, just a complete lack of sun is the issue. I'm in Shropshire.

Well then you could try the Cuppressus Wilma, or Bay trees - although the other day, Tesco's had some very reasonably priced standard hollies in pots, they were quite tall, about 3.5 feet including the pot.

There are varieties of holly that don't have prickles. Or you could buy a metal obelisk and train a variegated ivy around it, then keep it closely trimmed to look a bit like a topiary tree/bush. Ivy thrives in shade and can withstand neglect!!

Instead of small trees have you considered shrubs like Leucothoe 'Scarletta' for good winter leaf colour or Sarcococca, the Christmas box which will give flowers with a super scent at this time of the year? For a while you can plant seasonal bedding around the edges for extra interest.

Brilliant, many thanks for all your suggests - its really appreciated!

I have a similar entrance, north facing but very sheltered by the house. I have a Yew growing in a large pot - that covers evergreen and shade loving. They can be topiared to any shape, this time of year they tend to be cone shaped for Christmas. I also have Hostas growing in pots for spring and summer colours.