The bark looks normal, to me. Once the trunk and branches reach a certain size, the outermost bark flakes off, revealing different colored new bark underneath. The red leaves in such numbers are a little concerning, though. Unless they are acompanied by massive new growth, or are found on skinny, shaded twigs in the interior of the tree, they are symptoms of stress in the environment. Drought, lack of nutrients, or poor drainage are the commonest causes. It takes a lot of drought to stress a Eucalyptus, though!

Thank you Tugbrethil. From what you say, my guess would be poor drainage as our ground is heavy clay. At least there's hope for it with a bit of work - we've never grown it before and thought it was lost.

Check the soil pH. If it's low, add some limestone, and a little nitrogen: some clover hay, or fish meal, or blood meal. If it's high, add some gypsum. The calcium in the limestone or the gypsum will help open up the clay, over time, and low pH makes nitrogen less available to all plants. Most Eucalypts are tough and adaptable, so it probably just needs a little tweak to the soil.

I hope you have plenty of space, they get big, I have one now in a big pot but it's not happy, its dried out in summer.

Thanks again Tugbrethil. We'll check soil tomorrow and follow your advice.
Debsalison - We have the space for it. Just hope we can get it to thrive! Hope yours is okay too.

These are links to some information pages regarding growing eucalyptus in the UK:

https://www.hardy-eucalyptus.com/how-to-care-for-a-eucalyptus-plant

https://www.hardy-eucalyptus.com/where-to-plant

https://www.hardy-eucalyptus.com/training-and-pruning

Thank you Longleaf. Will have a read.