Our diesel ce'ed is really economical. We really like it.

I would spend £1-2000 on a diesel Peugeot, Skoda, or something japanese, join the AA and spend the rest on a holiday
The kids will remember the holiday for the rest of their lives but not the car

We had a Seat Ibiza when our two were small - great fun and steady on the motorway.

Honda Jazz
Citroen C3
Toyota Yaris

Personally I wouldn't have called a Fiesta mid-sized; Focus et al is nearer that size.

How many miles are your motorway commutes? Larger engines tend to suit motorway driving more than small engines - they won't be revving so high at motorway speeds so will be a lot less tiring (and possibly more economical) than a small engine buzzing away near the top of its performance range. If I take a mainly-motorway journey gently (60-65mph) in my 2.2 diesel, it displays up to 60mpg.

Focus is a safe bet, Skoda Octavia are well regarded for a cheaper brand and will give a bit more space in the boot (and some estates have 4x4 if that's an issue, but will knock the fuel economy a bit). Also worth looking at Honda Civic, Toyota Corolla - loads of options in this segment.

Toyota Yaris. I've had 3 kids (2 car seats) and a pram in mine.

I have an a classe which is great as it's a medium car, can get a buggy in the back, great to drive.

There's the new a classe that's bigger now too.

I live in somerset and would love a Volvo xc90, because of the extra seats and it's a 4x4 which is handy.

Have a look in which car? To see what you fancy.

I have a renault megane that really needs to go. I'm struggling to decide on something for me.

Dh has an audi a4 & his planned next car is an audi estate so we've got big family car covered.

We live in a rural area, i'd be using it for motorway driving (to/from work) so needs to be economical & I have a 2.5yo ds still in a stage 2 carseat & using a pushchair. We're also trying for another so may in the future need to be able to accommodate an infant seat.

I've been looking at mid sized cars eg kia ceed, ford fiesta/focus, vw golf, but worried about costs of running 2 'bigger' cars & thinking perhaps I should choose something smaller, but not sure a small car will accommodate pushchair etc or be so good for motorway driving. Budget around £10-15k.

Any recommendations for something suitable?