Hi Louis!
I am a Chartered Surveyor and a captain with a european airline.
You have done very well to be entering the final year of a 5 year construction related degree and still be only 21 years old (I was at least 5 years behind where you are now!), so all I can say is DO NOT QUIT UNIVERSITY NOW!!!!
Furthermore, once you have finished your degree DO NOT QUIT YOUR JOB!!!! Continue and finish your Assessment of Professional Competence with the RICS to obtain your full professional qualifications. You MUST do this now while you are young and all the knowledge is still fresh in your head. If you do not complete it now I guarantee you never will.... I have seen exactly this happen to friends and colleagues who still regret it years later.
Your professional qualification as a Chartered Surveyor will last you a life-time (provided you pay your RICS subscriptions and don't get dis-barred!).
A commercial flying licence (which is in NO WAY equivalent to a degree or a professional business qualification and don't let anyone tell you otherwise) can disappear at the drop of a hat and be gone forever.
Although I have not practised as a Surveyor for a few years and my knowledge may be a bit rusty, I know that I can always dust it off and return to the profession if I should need to in the future. That is my Plan "B", and you MUST have one in this industry which truly is in a shocking state. I mean, if you thought the construction industry is full of crooks and incompetents.....
Personally, I worked hard in the Surveying business for 12 or 13 years such that, just shy of my 33rd birthday, I was able to announce to my Partners that I was retiring from our Partnership to pursue my long held ambition to be a......you know what. Thence I trained debt free by the modular route while supported by what I had saved over the years.
You are quite correct in believing that the skills you learn in the construction industry will stand you in very good stead. The ability to identify and solve problems, communicate, manage and have a joke with people from all backgrounds, numeracy and literacy, business and commercial acumen (e.g. budget and time management) are, among others, all skills I brought with me and use every day.
At 21 you have plenty of time on your side so use it to your advantage. Fly along side your work by all means to obtain a PPL, but don't rush down to Oxford and hand over the price of a house no questions asked.....and as mentioned above, before committing any future savings to a commercial flight qualification invest in a day at Gatwick to obtain a Class 1 Medical. It's not cheap but it's worth it.
By the way, everything written in capital letters is my own emphasis, and I REALLY MEAN IT!
Good luck to you.