Although the MechEng course is pretty intense, it is a good idea to be involved in at least one extra-curricular activity. Personally, I found unlike school, studying all the time at university tends to be counter-productive- you end up spending more time making less progress than if you had just taken a break and come back to working. Especially if you are moving away from home, it is incredibly important to have some sort of extra-curricular unrelated to your degree to keep you sane.
One way you could do this is by taking a ‘Horizons’ course. For MechEng, in ME1 & ME2 (first and second year) any Horizons course you take will be for extra credit, though in ME3/4 (third and fourth year), it can count towards your degree.