It's possible but it also really depends on what course you're doing. For example, if you wanted a Computing & IT degree (like me!) there aren't any 60 point level 3 modules you could do and all of the 30 point modules only start in Jan or Feb, which could make for a very busy time. You'll need to look into the modules available and consider how you could split them up, e.g. level 1 & 2 in the first year, then a mixture of all 3 levels, then another mixture in the third year, so you have less pressure. If you could manage to get a level 1 module in each year then that would be helpful as they don't count towards your grade so you'd only need to pass those. However, some level 2/3 modules require the past experience and knowledge from level 1/2 modules, so again, you'd really need to think about the order.
Some people just can't cope with 120 points a year of study at all. Some do fine, and some just about manage with a lot of organisation. I've been doing 90 points a year whilst working full time and could have managed 120 of level 1 and 2, although I really wouldn't have wanted two exams in the same period (and have organised my study so I won't have that)...haven't yet started my level 3 modules but I'm splitting those over my last two years (taking me 4 years in total to get my degree) which I'm hoping I'll manage with fine.