Should I change job?

[Ukwhat?]

So, life dilema here.

First about us....
Me: I'm 27, I earn £40k as en engineer before tax about £28k after tax. Work contribute 6% into pension if I contribute 3%. I work 1 mile from home and cycle no matter the weather.
Wife: 27, Currently on maternity leave she works 3 days a week and earns about £19k before tax. Work contribute 14% into her pension in return for her contributing 7%. She works approx 1 mile from home and walks every day.
Us: 6 month old son, my wife will go back to work in 6 months. Goal is to become FI as early as possible (around 10 years probably) but not necessarily RE. Still 21 years left on mortgage if we made minimum payments. In the last 4 months we have reduced this down by 4 years by overpaying. We share one newish car that is 'very cheap to run'.

Situation....
I worked at company 1 and left to work for company 2 on a permanent basis, after 1 year I left company 2 to go back to work for company 1 for various reasons (mainly my wife was due to give birth and I wanted to be nearer to home) I'm now bored at work back at job 1 and becoming increasingly demotivated for various reasons.

An opportunity has appeared for me to do contracting work for a supplier where I would be doing the exact same role that I was doing at job 2. This is normally a 12 month contract with the possibility to extend. The pay before tax could range from £67k to £86k with the after tax income being £42k to £60k depending on IR35 status.

Downsides to new job...
Instead of working 1 mile away, this job would be a 60 mile daily total commute and is about 2 hours in total each day.
No permanent position, could be out of work after 1 year.
No sick pay
No work pension contributions.
No holiday pay.
Additional car costs.
Would need a 2nd car (15K miles per year)

Benefits to new job...
Significantly higher income, enabling FI earlier.
My own boss, I decide what work I do and do not accept and for what price I will work.
Can work from home 1 or 2 days a week.
Field I am more interested in.
Facilities no where near as good.

I can't move house as housing is significantly more expensive near the new job, we live in a good area that is very good value - it is also near to my wife work, and both of our parents (babysitting).

My question...
Simply, what should I do? How can I weigh this up and decide?
Should I risk it at the new job and suck up the longer days for a few years?
Should I stay where I am and just deal with a work place that isn't ideal but offers decent pay and benefits in relation to my costs and extra time I get at home?

Thank you for your help!

[MonkeyJenga]

Are there only two companies hiring engineers? I would look for higher pay closer to home.

[Ukwhat?]

Near here, there are a good few companies but all offer lower pay than what I am on. The job I am thinking about is not working for the company I worked for before, but it is for a supplier of that company and is based at the companies premises. There are multiple other suppliers I could work for with the same arrangement at the same premises.

[MonkeyJenga]

Oh, got it. So one of the negatives, that the job might end in 1 year, is partially offset by the chance to network at those other suppliers operating out of the same location?

I think you should run the numbers more thoroughly. How much would a car cost (purchase, gas, insurance, etc), how much are you giving up in pension, likelihood of being on the lower or higher end of the salary range, possible increased convenience costs, etc. Weigh the true salary increase against the time spent commuting.

[DebtFreeBy25]

If the financial variables for both positions were equal, would you still be interested in switching jobs? What is the value of your pension contributions, holidays and sick pay? How do you feel about driving? What value do you place on that additional commute time? It seems that you have a fair number of opportunities in your field, so potentially needing a new job in 12 months isn't huge risk. Factor in both personal and financial considerations when making this decision. 

The calculation for the new job would be:
Anticipated salary
- Car costs
- Value of your current pension contributions
- Value of sick days to you (Could be very little if you rarely use them)
- Value of your time commuting

On the other hand, your happiness is invaluable. If you feel that you would be happier in the other position and would make more money, then it seems like an easy choice.