Posted: 01/02/2013 at 00:54
You might find it easier to use landscape fabric to suppress the grass abd any weeds growing amongst it. Nothing will grow through that and you can cut slits into the fabric and put in shrubs or other plants (provided the soil is warm enough) and they will thus have a head start over the weeds. It is important to tuck the fabric back around the plant you have put in the hole and peg it in place with pieces of bent wire/ stones etc. Water can get in but plants cannot grow through it.
Covering the area you plan to plant with your new border with polythene can help to warm and dry out the soil to get it ready for seed sowing later. It's certainly cold and wet around this area and seeds will not germinate till the soil warms up.
Chiltern Seeds and Thompson and Morgan sell a great range of hardy annual and shrub seeds, some of which need the frost to break the dormancy so now can bee a good time to sow them and it can be fun to see what comes up. A great advantage is it's also cheaper!