What will you do there? Are you going to live alone?
More than focusing on the language only, make the most of the country. Travel whenever you can, go out, taste the food, if you like museums go to museums, learn whatever you can about the country, try to enjoy every day of your stay. Don’t stay home on the internet because you don’t feel like going out or feel tired. You don’t want to go back to the UK and think “I should have done that, and that, I should have visited that city, …”.
You’re likely to feel lonely at times, it’s never easy to be in a foreign country for a relatively long time, even more so if it’s your first time abroad and in such a different country. But don’t let that prevent you from making the most of your stay.
My first stay abroad (alone) was also the one I enjoyed the most. I did a work placement in Madrid, in a Spanish company. The first thing I looked for was an apartment with Spanish-speaking people. I got really lucky since I both had great roommates and wonderful colleagues. I learned a lot about Spain speaking with my colleagues, and a lot about Venezuela at home.
Where I was even luckier is that in summer in Spain, in most companies people work until 2:30 or 3pm and have the rest of the afternoon for themselves. So I had a lot of free time, and I really made the most of it. I traveled to other towns on every week-end, visited museums that helped me know Spain’s history better, got to know quite well the capital, spent afternoons with friends/colleagues/roommates. (I even went to a corrida but don’t tell anybody! ;)) I simply loved my stay there, and when I returned home I had no regret. There was still a lot of things I hadn’t done or didn’t know, yet I knew that I couldn’t have done more. Thanks to all that, my Spanish improved tremendously.
Unfortunately I can’t say the same about my stay in Portugal a few months later. Even if it was still a very good experience, I know I didn’t make the most of it that time.
You need a bit of luck but it’s mostly your own mindset that counts.