I'm sure this has been asked a million times already on here, so once more won't hurt with our particular set of circumstances.... 
The wife has had a new a car every 6 months for peanuts through my job for the past few years (I work in IT for a fleet management company) but as I'm changing job soon we need to buy her something.
She has a 60 mile daily commute at the moment, but we're looking to move as part of my new job next year and that will likely go down to 40 miles a day - all on A & B roads. She's had diesels up til now purely because they've cost the same for us as petrol cars and get better fuel economy. Now we're buying & maintaining ourselves though - I'm wondering if petrol may be the better option?
Considerations:
Diesels obviously cost more to buy, and with turbos, DPFs etc to go wrong over a petrol engine, am I right to avoid them even though they'll return better fuel economy for her commute?

The wife has had a new a car every 6 months for peanuts through my job for the past few years (I work in IT for a fleet management company) but as I'm changing job soon we need to buy her something.
She has a 60 mile daily commute at the moment, but we're looking to move as part of my new job next year and that will likely go down to 40 miles a day - all on A & B roads. She's had diesels up til now purely because they've cost the same for us as petrol cars and get better fuel economy. Now we're buying & maintaining ourselves though - I'm wondering if petrol may be the better option?
Considerations:
- £6k budget (can stretch this by £500 but ideally not).
- Needs to be safe & reliable as we have a 6 month old baby and she'll be taking her to nursery every morning.
- Reasonable boot to take a pram & associated baby gubbins.
- She's not really fussed about performance, as long as it's not completely rubbish.
- Planning to keep it for a good while all being well so preferably not lunar miles.
Diesels obviously cost more to buy, and with turbos, DPFs etc to go wrong over a petrol engine, am I right to avoid them even though they'll return better fuel economy for her commute?