Nope, not guaranteed the same amount every month on my miles I do, plus I don't it really covered the costs of some of my garage bills.
Definitely better off for me and my partner.
I'm unsure of how 45p isn't profitable?
Even when I had my s2000 I used to get paid 45p a mile and it was profitable.
So Profitable I used to jump at the chance of it.
200 miles = 90 quid and about 40 in fuel (I think)
8 trips would be a new set of tyres easily.
Less if going for budgets.
Im not even sure if 4k is as good as you think if you were getting paid that in mileage?
What was your average business miles a month?
Congratulations on new job!