Danny mate in my opinion I'd never consider a computer doing my pricing, don't even know if such software exists but youd end up in I right mess if it got it wrong.
I'll also say I've tried a couple of self employed quantity surveyors and paid them a couple of hundred quid for doing the pricing, and never won a single job any of them priced.
If the jobs more complex it's even more important imho to look at it yourself, go through it and price it yourself. That way at least if you get the job you've already got in your head what your up against.
I'm aware that that's not what you wanted to hear, but it's the my experience. Like you I'm onsite most of the time and it can be hard, it depends how hungry you are for work I guess, I've been know to spend brew time on the phone chasing prices of suppliers and all night going through drawings/putting quotes together. Nowadays if I'm that busy it'll put me out as a rule I turn it down, but I am backing off the throttle a touch as I get older and wanting a steadier life.