Bonsai advice?

I’ve always admired the art of bonsai. Something I’d like to start.
Some questions:

Trees of any age seem to be very expensive so I’d like to grow from seed or at most from young trees. Does anybody know a good seed supplier in the UK (or who ships to the UK at reasonable prices)?

What are the essential tools I need? There seems to be a bewildering array of things I could buy but I think I just need the basics at present.

I know that there are indoor and outdoor plants. I really like acers and Chinese elms which I’ve seen described as outdoor plants. It won’t harm them to grow them indoors will it? (I have no outdoors though my indoors is often quite cold if that makes a difference).

“Indoor” and “Outdoor” usually means, more accurately, “tropical” and “temperate,” respectively. You can’t grow temperate trees indoors, without sophisticated (i.e., expensive) temperature control ability. Temperate trees need a dormancy period; they need a winter. Tropical species are easier indoors, because they do not need a dormancy period.

Depending on your climate, you can keep temperate species outdoors. In Seattle, I have a metasequoia and a dwarf vine maple that have done pretty well for a few years. I’ve done any number of Ficus spp. indoors.

There are way lotta books; I recommend browsing a few. It’s one of the most information intensive hobbies this side of marine fish breeding.

Start with Ficus trees - they’re very durable and forgiving. Don’t get near the root ball until you know exactly what you’re doing. Don’t prune too much, or too drastically, or too often.

Also, bonzai and small animals or children don’t mix well.