Thanks for the input ladies - you've all given me good points to consider.
Last night, as I lay awake fretting (!), I began to think that perhaps it would be irresponsible of me to quit right now.
As you say Lulu, the job is good for a number of reasons, and MR, yes, I think DS is happy with the current situation. Really he gets the best of both worlds. You're right Fiona, it is like having 2 jobs - I'm a full-time earner and a part-time mum!
I have time to think some more and won't make any rash decisions. With the recession, if I quit, I won't have a job to come back to or anything...
Thanks again