Piper,
First the disclaimer - I went to college in Dublin and I teach labs in Dublin - the UK may be different.
I got my degree in Engineering. Second-highest workload in the college (only Medical students were working harder and they're unbalanced
) but 2 hours a night would have been major overkill for the first two or three years, with the exception of that last month before the exams, and the scholarship exams I studied for in second year. Frankly, so long as you're not falling asleep in lectures, 30-60 minutes during the day rereading your lecture notes was enough to ensure firsts unless you came across something that really nobbles your head (for some reason ODE's never went into my head right, even after weeks of banging my head off them in the library), and those 30-60 minutes can be split - reread your morning notes over lunch and your evening notes on the bus/train home. Me, I tended to read the notes all in one go, but I had a 90 minute trip home each day - sort of enforced study time
That said - don't plan on having any time or social life at ALL in final year. Some people in my year managed to keep a social life up to christmas of final year, but only because they were dedicated to it
The rest of us slobs just said good-bye to the world and lived in the college (by which I don't mean having rooms there, I mean I would spend about 7-8 hours out of 24 at home every weekday, and usually spent the majority of weekends in college, along with the few 24-hour sessions needed on some labs
Still remember being woken up by the cleaning crew because I was drooling into the keyboard in my sleep
) Plus, you have to find time in there to fit in a physically active sport - healthy body being bloody necessary to survive college and avoid the bloating that often arises from living off vending machines because the coffee shop stopped serving ham sandwiches two hours ago and you didn't remember your packed lunch that day because you figured the extra half-hour of sleep was more important the night before
Again, remember, this is engineering in Trinity College Dublin - your milage may vary. Try talking to recently graduated students from your uni if you can locate any - the lecturers, sadly, will not be of use on this point!