As they currently are, they look like they need some kind of support, especially that taller one. I think they have become too tall and straggly for the present trunks to become self-supporting, especially the taller one, so some surgery to reshape them will be necessary, but it is important first for them to become well-rooted in the ground. When you feel they are well-established (evidence of healthy growth) then wait until the next spring and then shorten them. Just cut the whole top somewhere like knee height to waist height, with an angle to the cut. They will send out lots of shoots from the stump, which you can then thin out if necessary. You are going to get a tree that branches out low down rather than a single stem, but basically this is the only choice you have if you want a tree that doesn't grow big. You'll have to give it a good prune every now and then to keep it to the size you want. You are going to have to make some kind of drastic action like this anyway in the long run to prevent them becoming big trees, so may as well start as you intend to go on.

I rescued a few tall thin and straggly pot-bound eucs from a euc nursery that was closing down, and treated as I described above, and they have all survived.

There are actually about 100 Euc species you can grow in Britain, yet mostly you only see about 3 or 4 species in most garden centres. The common ones are mostly huge, like gunnii, perriniana, glaucescens and dalrympleana, which is a shame as there are plenty of others that are more manageable garden trees that are seen less often. Nipophila (strictly pauciflora subsp nipophila) is probably the only smaller one that is anything like fairly easy to get (says he taking a quick look at RHS plantfinder). I'm growing mannifera subsp praecox, nova-anglica and pulverulenta - the first two are very rare in cultivation in Britian (RHS notes them as no longer listed). As I said, nipophila is the most commonly seen smaller Euc, but in my view the closely related pauciflora subsb pauciflora, and gregsoniana are more desirable. Crenulata is also a stunner. Pulverulenta is very non-typical, it is the one grown as foliage for the cut-flower trade, for which frequent cutting is necessary to get the right habit, a bush rather than a tree when grown like this. I'm growing the nova-anglica in the same fashion, it's a real beauty. Since it's the juvenile leaves that are so nice, its important to keep it cut back to retain them. In fact you can say the same of many eucs, like perriniana.