Where in England? I am in Westbury in Wiltshire. Hornbeam can be good, or Scots pine, Mugo Pine, Maples Branches can be grown so the trunk is the most important part. Have a look at bonsai4me.com very good species guides etc, Harry has written two very good books.
Use a free draining soil, so John Innes 3 with Cornish grit if you can get it at about 30% You can't do any re potting now of course, until next spring.
Depending on where you are you could be near a bonsai nursery.
If you can find an ungrafted one I would look for a Maple. If they are grafted then look for a low graft and make sure that the graft and top are the same colour.
The best place for a young tree to grown on is planted in the ground, by far the quickest way to get girth on the trunk.
If you can't put it in the ground then a big pot will do.
Geoff.