Hmmm, depends how much debt you want to carry around. Figure on leaving uni with 15-20K minimum and then anywhere from 50-70K if you need to pay your own way through flight school (likely if sponsorship is hard to come by).
Advice: Well, do the degree. Uni is bloody good fun and gives you a few more years worth of experience to take forward. Also, possible alternative career if flying goes tits up, but don't count on it as a certainty. No guaranteed jobs for graduates of unis any more than graduates of flight schools, but engineering is a good choice as long as you keep your knowledge current.
Take a part time job and get in some flying at weekends or something, just so you can show an interest beyond looking at aeroplanes, but don't stress about actually getting a PPL as you end up going over the same ground again at flight school, so possibly just wasted money. Spend it on as many hours as you can get. UAS a good idea if you want to fly sexy and exciting things, but if you want to fly airlines then there is a good chance you will be winkled out at selection. The RAF don't take kindly to paying for your flying if you wont sign on the dotted line.
Apply for sponsorships, some are on the go right now, and I'm sure despite the gloom merchants that the likes of BA will restart again - it's their preferred route for recruitment. Keep an eye on the aviation press, especially the small ads at the back, and a beady eye on pprune for rumours. Contact airlines now to see what requirements are and keep in contact on a regular basis - another way of showing an interest other than flying.
Difficult time to be going into it, but at least now you can see the potential pitfalls of the career. Weigh up the huge potential costs involved against your likelihood of getting in and paying them off if you don't.