Would you pay to fix up your old runaround

[Lorddenning1]

My 2004 Corsa broke down yesterday, the garage has fixed the car at a cost of £56, which isn't bad, however he has noticed the car needs more work, it's currently mis firing (news to me) I have it book in for its MOT in a couple of weeks and I have been told it will fail, due to this fault, so for the MOT and the mis fire it will cost £150 to fix, this isn't including anything else it might fail on, the car is only worth £600 anyways. So my options are, to pay for the £150 and anything else it needs or take out a loan for £2,000 and get a new car, repayment of the loan will be around £50 a month for 4 years (we can just about manage this).
We only have the one car and I need it for work, I personally don't like the car, it's too small for a family of 4 and to make things worst it's only 3 doors so it's hard to put the kids in and out, but I'm trying to not let this rule my judgement. What should I do, what's the most practical thing to do, we don't have a lot of money, we are just about managing due to high child care costs, but that's a different thread.

Was the cause of the misfire a faulty coil pack? On a Corsa the coil pack is only £40 then about £9 for all 4 (or 3 if it's 1 litre 3 cylinder) spark plugs. £150 seems VERY steep to fix a misfire unless one of the cylinders was losing compression

@Rosicky07 £150 included an MOT also, I spent a total of £418 as it failed its MOT and had various problems etc, the coil pack was £80 and the sparks plugs were £18.
A family member has kindly given me a new car, it's a 5 door saloon, good miles, not too old, great condition, how nice is that, it's perfect for our family, plus I will sell the Corsa and hopefully will get the money we paid to fix it back hard work does pay off