It depends on what kind of work philosophy you have.
If you absolutely must take 25 bits of hand kit around with you just in case you need them, you're going to need a decent sized van. But if you manage to scrape by with just the bare essentials then it'll be fine. Obviously the less kit you have the less able you are to deal with every eventuality, which may lead to corner-cutting.
There's a photo of someone's truckmount on another thread, installed in a SWB low roof transit. It completely fills the load space, he can't even get his solution hose reel in there! Throw stones at me if you like but that's bad planning. Yes, there is some space left but it's not very useable space. If you want whatever's at the back you have to move what's in front of it.
I know this problem well, because I prefer to be over-equipped rather than need something I haven't got half way through as job - what use is a tool if it's sitting at home in the garage?. I run a Scudo with enough kit in it to fill a lorry
You value space more, the less of it you have.
One important point has already been mentioned, but this could save your life so I'll reiterate. Estate cars are DANGEROUS to carry heavy objects such as extraction machines around in. Imagine a head-on impact... The driving seat isn't going to afford you any sort of protection from flying machinery or tools, even a hand tool could seriously hurt you.
Vans have a steel bulkhead or at least a framework behind the seats, to cut this risk down.
A tidy, sign-written van looks infinitely more professional than a family car.
I'm not encouraging you to run out and get a van on HP and spend thousands but I definitely think it should be high on your priority list