The trees will be fine in the blister pack for several days but then they will need watering.
Within a few weeks the trees should be potted on into a quite large pot, say 8" to 12" diameter. Place a layer of stones or gravel in the bottom of the pot for drainage and then fill the pot with good garden soil. If your soil is very heavy clay you might mix in some coarse sand but most soils will be fine. Position the tree seedling at the centre of the pot and firm the soil around it.
Place the pot outside where it will get the sun and rain. Put it in your garden or on your terrace or balcony even a window sill (make sure it will not fall on someone). Ideally it should be located in a spot which is shady for most of the day but does get some sunshine for a few hours. Water it once and more or less forget about it. It will look after itself. The large pot will mean that the rain will be sufficient to keep it moist most of the time. If there is a prolonged period without rain then it will need you to water it. Plastic pots retain water much better than clay pots but they do not look so nice.
After 2 or 3 years the tree should be 2ft to 3ft high, now it is time to plant it in its permanent position.
If you have room in your garden and if you are likely to stay in that property for sometime then it might be nice to plant it in the garden where you can enjoy it in its young years (NB Tree roots spread out almost as far as the tree will grow in height, so do not plant it close to any buildings).
Alternatively plant it out in the countryside. To find a suitable place where it is not going to get cut down you could contact your local wildlife trust or a farmer or the borough council in the area you intent to plant it.
Once it is planted out (best time to do this is early Spring) do not forget to complete your Certificate of Provenance with the trees location.
Once your tree is in its final location you might like to place a plaque infront of it with a small amount of information about the tree,such as 'Caroline and Felix married Oxford 2006' . If this is made from a fairly durable wood then it will survive many years though possibly not as long as the tree itself. One supplier of such plaques is www.timbertags.com
These trees are all British trees so they are not difficult to grow as they are adapted to our conditions. However they will also become homes for many other species. Do not be alarmed if some of the leaves get eaten, there is a good chance that spots and blemishes will also develop on the leaves caused by fungi, galls and leaf miners. This is all quite natural and good, you are not planting just a tree you are creating a complete micro habitat.