Depends on the course and your commitment
I did a four year part time course while working full time – employers paid for 3 out of the four years. It was relatively easy – the first two years I was just over the grade for a first.
Three bits of advice:
1) Ensure that your other half is 100% behind your effort, why you are doing it, what you intend to get out of it. You will both have to commit to it.
2) Don't arrange to get married at the end of your first year.
3) Don't have a baby at the end of your second year.
Studying and working I could cope with, but doing both with a baby/toddler in the house and very little sleep was a bit more problematic. In the end I missed out on a 2:1 by 1-2% points, which in the current climate makes my efforts and my degree worth pretty much naff all!