fine that you keep your Estrella!
Do you want to move it from Sweden to Wales???
An Estrella is reliable as any other modern motorbike!
The only thing you should do: Treat her like an Estrella!!!
What do I mean?
The travelling speed should be somewhere between 80 and 90 kmph. You can sometimes ride 100 or 110, but only short passages.
If you never had any oil problem, you don't need to take care of anything. My BJ250C doesn't need any extra oil for more than 3000 km. I rode with her to the Fishhead-Tour in Northern Germany last year. Three days. 330 km, 150 km tour, 330 km back. No problem! Especially the C-Version with her bench is fitted for long terms. It has a better seat than some other bikes!
A problem I had before was, that I lost screws form the indicator switch. So, you should have a short look if all screws are tightened. But that can happen to every motorbike after 7 years!
So, if you take it slow, there is nothing special you have to care about! The Estrella is 100% reliable. You should take some wires with you if something removes, maybe some fuses and a role of tape (if something removes or electrical problems). You should of course look for the oil and tire pressure.
But this is not Estrella typical - more unversal for a motorbike trip!!!
Oh yes; a camera is a MUST! You need to make photos of your tour to show us!
A report would also be fine - so maybe a biro and a piece of paper?!
A pair of AIDS- / rubber gloves might be good if it's very rainy! You can put them on under your normal motorbike gloves. Keeps your hands warm and dry while heavy rain - which is very important. On long term rides, I also take some cotton wool for my ears with me. The permanent noise for 6 or 8 hours might attack your ears! You can get special ear plugs in music or motorbike shops, too. They filter the noise in a much better spectrum than cheap cotton wool!